Solid-state drive


A solid-state drive is a solid-state storage device that uses integrated circuit assemblies to store data persistently, typically using flash memory, and functioning as secondary storage in the hierarchy of computer storage. It is also sometimes called a solid-state device or a solid-state disk, even though SSDs lack the physical spinning disks and movable read–write heads used in hard drives or floppy disks.
Compared with the electromechanical drives, SSDs are typically more resistant to physical shock, run silently, and have quicker access time and lower latency. SSDs store data in semiconductor cells. As of 2019, cells can contain between 1 and 4 bits of data. SSD storage devices vary in their properties according to the number of bits stored in each cell, with single-bit cells being generally the most reliable, durable, fast, and expensive type, compared with 2- and 3-bit cells, and finally quad-bit cells being used for consumer devices that do not require such extreme properties and are the cheapest of the four. In addition, 3D XPoint memory, stores data by changing the electrical resistance of cells instead of storing electrical charges in cells, and SSDs made from RAM can be used for high speed, when data persistence after power loss is not required, or may use battery power to retain data when its usual power source is unavailable. Hybrid drives or solid-state hybrid drives, such as Apple's Fusion Drive, combine features of SSDs and HDDs in the same unit using both flash memory and a HDD in order to improve the performance of frequently-accessed data.
While the price of SSDs has continued to decline over time, SSDs are still more expensive per unit of storage than HDDs and are expected to remain so into the next decade.
SSDs based on NAND Flash will slowly leak charge over time if left for long periods without power. This causes worn-out drives to start losing data typically after one year to two years in storage; for new drives it takes longer. Therefore, SSDs are not suitable for archival storage. 3D XPoint is a possible exception to this rule, however it is a relatively new technology with unknown long-term data-retention characteristics.
SSDs can use traditional hard disk drive interfaces and form factors, or newer interfaces and form factors that exploit specific advantages of the flash memory in SSDs. Traditional interfaces and standard HDD form factors allow such SSDs to be used as drop-in replacements for HDDs in computers and other devices. Newer form factors such as mSATA, M.2, U.2, NF1, XFMEXPRESS and EDSFF and higher speed interfaces such as NVMe over PCI Express can further increase performance over HDD performance.

Development and history

Early SSDs using RAM and similar technology

An early—if not the first—semiconductor storage device compatible with a hard drive interface was the 1978 StorageTek STC 4305. The STC 4305, a plug-compatible replacement for the IBM 2305 fixed head disk drive, initially used charge-coupled devices for storage and consequently was reported to be seven times faster than the IBM product at about half the price It later switched to DRAM. Before the StorageTek SSD there were many DRAM and core products sold as alternatives to HDDs but these products typically had memory interfaces and were not SSDs as defined.
In the late 1980s, Zitel offered a family DRAM based SSD products, under the trade name "RAMDisk," for use on systems by UNIVAC and Perkin-Elmer, among others.

Flash-based SSDs

The basis for flash-based SSDs, flash memory, was invented by Fujio Masuoka at Toshiba in 1980 and commercialized by Toshiba in 1987. SanDisk Corporation founders Eli Harari and Sanjay Mehrotra, along with Robert D. Norman, saw the potential of flash memory as an alternative to a hard drive, and filed a patent for a flash-based SSD in 1989. The first commercial flash-based SSD was shipped by SunDisk in 1991. It was a 20 MB SSD in a PCMCIA configuration, and sold OEM for around $1,000 and was used by IBM in a ThinkPad laptop. In 1998, SanDisk introduced SSDs in 2½ and 3½ form factors with PATA interfaces.
In 1995, STEC, Inc. entered the flash memory business for consumer electronic devices.
In 1995, M-Systems introduced flash-based solid-state drives as HDD replacements for the military and aerospace industries, as well as for other mission-critical applications. These applications require the SSD's ability to withstand extreme shock, vibration and temperature ranges.
In 1999, BiTMICRO made a number of introductions and announcements about flash-based SSDs, including an 18 GB 3.5-inch SSD. In 2007, Fusion-io announced a PCIe-based Solid state drive with 100,000 input/output operations per second of performance in a single card, with capacities up to 320 GB.
At Cebit 2009, OCZ Technology demonstrated a 1 TB flash SSD using a PCI Express ×8 interface. It achieved a maximum write speed of 0.654 gigabytes per second and maximum read speed of 0.712 GB/s. In December 2009, Micron Technology announced an SSD using a 6 gigabits per second SATA interface.
In 2016, Seagate demonstrated 10 GB/S sequential read and write speeds from a 16-lane PCIe 3.0 SSD and also demonstrated a 60 TB SSD in a 3.5-inch form factor. Samsung also launched to market a 15.36TB SSD with a price tag of US$10,000 using a SAS interface, using a 2.5-inch form factor but with the thickness of 3.5-inch drives. This was the first time a commercially available SSD had more capacity than the largest currently available HDD.
In 2018, both Samsung and Toshiba introduced to market 30.72 TB SSDs using the same 2.5-inch form factor but with 3.5-inch drive thickness using a SAS interface. Nimbus Data announced and reportedly shipped 100 TB drives using a SATA interface, a capacity HDDs are not expected to reach until 2025. Samsung introduced an M.2 NVMe SSD with read speeds of 3.5 GB/s and write speeds of 3.3 GB/s. A new version of the 100TB SSD was launched in 2020 at a price of US$40,000, with the 50 TB version costing US$12,500.
In 2019, Gigabyte Technology demonstrated an 8 TB 16-lane PCIe 4.0 SSD with 15.0 GB/s sequential read and 15.2 GB/s sequential write speeds at Computex 2019. It included a fan, as new, high speed SSDs run at high temperatures. Also in 2019, NVMe M.2 SSDs using the PCIe 4.0 interface were launched. These SSDs have read speeds of up to 5.0 GB/s and write speeds of up to 4.4 GB/s. Due to their high speed operation, these SSDs use large heatsinks, and if they do not receive sufficient cooling airflow will typically thermally throttle down after roughly 15 minutes of continuous operation at full speed. Samsung also introduced SSDs capable of 8 GB/s sequential read and write speeds and 1.5 million IOPS, capable of moving data from damaged chips to undamaged chips, to allow the SSD to continue working normally, albeit at a lower capacity.

Enterprise flash drives

Enterprise flash drives are designed for applications requiring high I/O performance, reliability, energy efficiency and, more recently, consistent performance. In most cases, an EFD is an SSD with a higher set of specifications, compared with SSDs that would typically be used in notebook computers. The term was first used by EMC in January 2008, to help them identify SSD manufacturers who would provide products meeting these higher standards. There are no standards bodies who control the definition of EFDs, so any SSD manufacturer may claim to produce EFDs when in fact the product may not actually meet any particular requirements.
An example is the Intel DC S3700 series of drives, introduced in the fourth quarter of 2012, which focuses on achieving consistent performance, an area that had previously not received much attention but which Intel claimed was important for the enterprise market. In particular, Intel claims that, at a steady state, the S3700 drives would not vary their IOPS by more than 10–15%, and that 99.9% of all 4 KB random I/Os are serviced in less than 500 µs.
Another example is the Toshiba PX02SS enterprise SSD series, announced in 2016, which is optimized for use in server and storage platforms requiring high endurance from write-intensive applications such as write caching, I/O acceleration and online transaction processing. The PX02SS series uses 12 Gbit/s SAS interface, featuring MLC NAND flash memory and achieving random write speeds of up to 42,000 IOPS, random read speeds of up to 130,000 IOPS, and endurance rating of 30 drive writes per day.
SSDs based on 3D XPoint have higher random but lower sequential read/write speeds than their NAND-flash counterparts. They can have up to 2.5 million IOPS.

Drives using other persistent memory technologies

In 2017, the first products with 3D Xpoint memory were released under Intel's Optane brand. 3D Xpoint is entirely different from NAND flash and stores data using different principles.

Architecture and function

The key components of an SSD are the controller and the memory to store the data. The primary memory component in an SSD was traditionally DRAM volatile memory, but since 2009 it is more commonly NAND flash non-volatile memory.

Controller

Every SSD includes a controller that incorporates the electronics that bridge the NAND memory components to the host computer. The controller is an embedded processor that executes firmware-level code and is one of the most important factors of SSD performance. Some of the functions performed by the controller include:
The performance of an SSD can scale with the number of parallel NAND flash chips used in the device. A single NAND chip is relatively slow, due to the narrow asynchronous I/O interface, and additional high latency of basic I/O operations. When multiple NAND devices operate in parallel inside an SSD, the bandwidth scales, and the high latencies can be hidden, as long as enough outstanding operations are pending and the load is evenly distributed between devices.
Micron and Intel initially made faster SSDs by implementing data striping and interleaving in their architecture. This enabled the creation of ultra-fast SSDs with 250 MB/s effective read/write speeds with the SATA 3 Gbit/s interface in 2009. Two years later, SandForce continued to leverage this parallel flash connectivity, releasing consumer-grade SATA 6 Gbit/s SSD controllers which supported 500 MB/s read/write speeds. SandForce controllers compress the data before sending it to the flash memory. This process may result in less writing and higher logical throughput, depending on the compressibility of the data.

Wear leveling

If a particular block is programmed and erased repeatedly without writing to any other blocks, that block will wear out before all the other blocks — thereby prematurely ending the life of the SSD. For this reason, SSD controllers use a technique called wear leveling to distribute writes as evenly as possible across all the flash blocks in the SSD.
In a perfect scenario, this would enable every block to be written to its maximum life so they all fail at the same time. The process to evenly distribute writes requires data previously written and not changing to be moved, so that data which are changing more frequently can be written into those blocks. Relocating data increases write amplification and adds to the wear of flash memory. Designers seek to minimize both.

Memory

Flash memory

Most SSD manufacturers use non-volatile NAND flash memory in the construction of their SSDs because of the lower cost compared with DRAM and the ability to retain the data without a constant power supply, ensuring data persistence through sudden power outages. Flash memory SSDs were initially slower than DRAM solutions, and some early designs were even slower than HDDs after continued use. This problem was resolved by controllers that came out in 2009 and later.
Flash-based SSDs store data in metal-oxide-semiconductor integrated circuit chips which contain non-volatile floating-gate memory cells. Flash memory-based solutions are typically packaged in standard disk drive form factors, but also in smaller more compact form factors, such as the M.2 form factor, made possible by the small size of flash memory.
Lower-priced drives usually use triple-level cell or multi-level cell flash memory, which is slower and less reliable than single-level cell flash memory. This can be mitigated or even reversed by the internal design structure of the SSD, such as interleaving, changes to writing algorithms, and higher over-provisioning with which the wear-leveling algorithms can work.
Solid-state drives that rely on V-NAND technology, in which layers of cells are stacked vertically, have been introduced.

DRAM

SSDs based on volatile memory such as DRAM are characterized by very fast data access, generally less than 10 microseconds, and are used primarily to accelerate applications that would otherwise be held back by the latency of flash SSDs or traditional HDDs.
DRAM-based SSDs usually incorporate either an internal battery or an external AC/DC adapter and backup storage systems to ensure data persistence while no power is being supplied to the drive from external sources. If power is lost, the battery provides power while all information is copied from random access memory to back-up storage. When the power is restored, the information is copied back to the RAM from the back-up storage, and the SSD resumes normal operation.
SSDs of this type are usually fitted with DRAM modules of the same type used in regular PCs and servers, which can be swapped out and replaced by larger modules.
Such as i-RAM, HyperOs HyperDrive, DDRdrive X1, etc.
Some manufacturers of DRAM SSDs solder the DRAM chips directly to the drive, and do not intend the chips to be swapped out—such as ZeusRAM, Aeon Drive, etc.
A remote, indirect memory-access disk uses a secondary computer with a fast network or Infiniband connection to act like a RAM-based SSD, but the new, faster, flash-memory based, SSDs already available in 2009 are making this option not as cost effective.
While the price of DRAM continues to fall, the price of Flash memory falls even faster.
The "Flash becomes cheaper than DRAM" crossover point occurred approximately 2004.

3D XPoint

In 2015, Intel and Micron announced 3D XPoint as a new non-volatile memory technology. Intel released the first 3D XPoint-based drive in March 2017 starting with data center product - Intel® Optane™ SSD DC P4800X Series, and following with the client version - Intel® Optane™ SSD 900P Series in October 2017. Both products operate faster and with higher endurance than NAND-based SSDs, while the areal density is comparable at 128 gigabits per chip. For the price per bit, 3D XPoint is more expensive than NAND, but cheaper than DRAM.

Other

Some SSDs, called NVDIMM or Hyper DIMM devices, use both DRAM and flash memory. When the power goes down, the SSD copies all the data from its DRAM to flash; when the power comes back up, the SSD copies all the data from its flash to its DRAM. In a somewhat similar way, some SSDs use form factors and buses actually designed for DIMM modules, while using only flash memory and making it appear as if it were DRAM. Such SSDs are usually known as ULLtraDIMM devices.
Drives known as hybrid drives or solid-state hybrid drives use a hybrid of spinning disks and flash memory. Some SSDs use magnetoresistive random-access memory for storing data.

Cache or buffer

A flash-based SSD typically uses a small amount of DRAM as a volatile cache, similar to the buffers in hard disk drives. A directory of block placement and wear leveling data is also kept in the cache while the drive is operating. One SSD controller manufacturer, SandForce, does not use an external DRAM cache on their designs but still achieves high performance. Such an elimination of the external DRAM reduces the power consumption and enables further size reduction of SSDs.

Battery or supercapacitor

Another component in higher-performing SSDs is a capacitor or some form of battery, which are necessary to maintain data integrity so the data in the cache can be flushed to the drive when power is lost; some may even hold power long enough to maintain data in the cache until power is resumed. In the case of MLC flash memory, a problem called lower page corruption can occur when MLC flash memory loses power while programming an upper page. The result is that data written previously and presumed safe can be corrupted if the memory is not supported by a supercapacitor in the event of a sudden power loss. This problem does not exist with SLC flash memory.
Most consumer-class SSDs do not have built-in batteries or capacitors; among the exceptions are the Crucial M500 and MX100 series, the Intel 320 series, and the more expensive Intel 710 and 730 series. Enterprise-class SSDs, such as the Intel DC S3700 series, usually have built-in batteries or capacitors.

Host interface

The host interface is physically a connector with the signalling managed by the SSD's controller. It is most often one of the interfaces found in HDDs. They include:
SSDs support various logical device interfaces, such as Advanced Host Controller Interface and NVM Express. Logical device interfaces define the command sets used by operating systems to communicate with SSDs and host bus adapters.

Configurations

The size and shape of any device is largely driven by the size and shape of the components used to make that device. Traditional HDDs and optical drives are designed around the rotating platter or optical disc along with the spindle motor inside. If an SSD is made up of various interconnected integrated circuits and an interface connector, then its shape is no longer limited to the shape of rotating media drives. Some solid state storage solutions come in a larger chassis that may even be a rack-mount form factor with numerous SSDs inside. They would all connect to a common bus inside the chassis and connect outside the box with a single connector.
For general computer use, the 2.5-inch form factor is the most popular. For desktop computers with 3.5-inch hard disk drive slots, a simple adapter plate can be used to make such a drive fit. Other types of form factors are more common in enterprise applications. An SSD can also be completely integrated in the other circuitry of the device, as in the Apple MacBook Air., mSATA and M.2 form factors also gained popularity, primarily in laptops.

Standard HDD form factors

The benefit of using a current HDD form factor would be to take advantage of the extensive infrastructure already in place to mount and connect the drives to the host system. These traditional form factors are known by the size of the rotating media, e.g., 5.25-inch, 3.5-inch, 2.5-inch, 1.8-inch, not by the dimensions of the drive casing.

Standard card form factors

For applications where space is at premium, like for ultrabooks or tablet computers, a few compact form factors were standardized for flash-based SSDs.
There is the mSATA form factor, which uses the PCI Express Mini Card physical layout. It remains electrically compatible with the PCI Express Mini Card interface specification, while requiring an additional connection to the SATA host controller through the same connector.
M.2 form factor, formerly known as the Next Generation Form Factor, is a natural transition from the mSATA and physical layout it used, to a more usable and more advanced form factor. While mSATA took advantage of an existing form factor and connector, M.2 has been designed to maximize usage of the card space, while minimizing the footprint. The M.2 standard allows both SATA and PCI Express SSDs to be fitted onto M.2 modules.

Disk-on-a-module form factors

A disk-on-a-module is a flash drive with either 40/44-pin Parallel ATA or SATA interface, intended to be plugged directly into the motherboard and used as a computer hard disk drive. DOM devices emulate a traditional hard disk drive, resulting in no need for special drivers or other specific operating system support. DOMs are usually used in embedded systems, which are often deployed in harsh environments where mechanical HDDs would simply fail, or in thin clients because of small size, low power consumption and silent operation.
, storage capacities range from 4 MB to 128 GB with different variations in physical layouts, including vertical or horizontal orientation.

Box form factors

Many of the DRAM-based solutions use a box that is often designed to fit in a rack-mount system. The number of DRAM components required to get sufficient capacity to store the data along with the backup power supplies requires a larger space than traditional HDD form factors.

Bare-board form factors

Form factors which were more common to memory modules are now being used by SSDs to take advantage of their flexibility in laying out the components. Some of these include PCIe, mini PCIe, mini-DIMM, MO-297, and many more. The SATADIMM from Viking Technology uses an empty DDR3 DIMM slot on the motherboard to provide power to the SSD with a separate SATA connector to provide the data connection back to the computer. The result is an easy-to-install SSD with a capacity equal to drives that typically take a full 2.5-inch drive bay. At least one manufacturer, Innodisk, has produced a drive that sits directly on the SATA connector on the motherboard without any need for a power cable. Some SSDs are based on the PCIe form factor and connect both the data interface and power through the PCIe connector to the host. These drives can use either direct PCIe flash controllers or a PCIe-to-SATA bridge device which then connects to SATA flash controllers.

Ball grid array form factors

In the early 2000s, a few companies introduced SSDs in Ball Grid Array form factors, such as M-Systems' DiskOnChip and Silicon Storage Technology's NANDrive, and Memoright's M1000 for use in embedded systems. The main benefits of BGA SSDs are their low power consumption, small chip package size to fit into compact subsystems, and that they can be soldered directly onto a system motherboard to reduce adverse effects from vibration and shock.
Such embedded drives often adhere to the eMMC and eUFS standards.

Comparison with other technologies

Hard disk drives

Making a comparison between SSDs and ordinary HDDs is difficult. Traditional HDD benchmarks tend to focus on the performance characteristics that are poor with HDDs, such as rotational latency and seek time. As SSDs do not need to spin or seek to locate data, they may prove vastly superior to HDDs in such tests. However, SSDs have challenges with mixed reads and writes, and their performance may degrade over time. SSD testing must start from the full drive, as the new and empty drive may have much better write performance than it would show after only weeks of use.
Most of the advantages of solid-state drives over traditional hard drives are due to their ability to access data completely electronically instead of electromechanically, resulting in superior transfer speeds and mechanical ruggedness. On the other hand, hard disk drives offer significantly higher capacity for their price.
Some field failure rates indicate that SSDs are significantly more reliable than HDDs but others do not. However, SSDs are uniquely sensitive to sudden power interruption, resulting in aborted writes or even cases of the complete loss of the drive. The reliability of both HDDs and SSDs varies greatly among models.
As with HDDs, there is a tradeoff between cost and performance of different SSDs. Single-level cell SSDs, while significantly more expensive than multi-level SSDs, offer a significant speed advantage. At the same time, DRAM-based solid-state storage is currently considered the fastest and most costly, with average response times of 10 microseconds instead of the average 100 microseconds of other SSDs. Enterprise flash devices are designed to handle the demands of tier-1 application with performance and response times similar to less-expensive SSDs.
In traditional HDDs, a rewritten file will generally occupy the same location on the disk surface as the original file, whereas in SSDs the new copy will often be written to different NAND cells for the purpose of wear leveling. The wear-leveling algorithms are complex and difficult to test exhaustively; as a result, one major cause of data loss in SSDs is firmware bugs.
The following table shows a detailed overview of the advantages and disadvantages of both technologies. Comparisons reflect typical characteristics, and may not hold for a specific device.
Attribute or characteristicSolid-state driveHard disk drive
Price per capacitySSDs generally are more expensive than HDDs and expected to remain so into the next decade.
SSD price as of first quarter 2018 around 30 cents per gigabyte based on 4 TB models.
Prices have generally declined annually and as of 2018 are expected to continue to do so.
HDD price as of first quarter 2018 around 2 to 3 cents per gigabyte based on 1 TB models.
Prices have generally declined annually and as of 2018 are expected to continue to do so.
Storage capacityIn 2018, SSDs were available in sizes up to 100 TB, but less costly, 120 to 512 GB models were more common.In 2018, HDDs of up to 16 TB were available.
Reliability – data retentionIf left without power, worn out SSDs typically start to lose data after about one to two years in storage, depending on temperature. New drives are supposed to retain data for about ten years. MLC and TLC based devices tend to lose data earlier than SLC-based devices. SSDs are not suited for archival use.If kept in a dry environment at low temperature, HDDs can retain their data for a very long period of time even without power. However, the mechanical parts tend to become clotted over time and the drive fails to spin up after a few years in storage.
Reliability – longevitySSDs have no moving parts to fail mechanically so in theory should be more reliable than HDDs. However, in practice this is unclear,
Each block of a flash-based SSD can only be erased a limited number of times before it fails. The controllers manage this limitation so that drives can last for many years under normal use. SSDs based on DRAM do not have a limited number of writes. However the failure of a controller can make an SSD unusable. Reliability varies significantly across different SSD manufacturers and models with return rates reaching 40% for specific drives. Many SSDs critically fail on power outages; a December 2013 survey of many SSDs found that only some of them are able to survive multiple power outages.
A Facebook study found that sparse data layout across an SSD's physical address space, dense data layout and higher operating temperature each lead to increased failure rates among SSDs.
However, SSDs have undergone many revisions that have made them more reliable and long lasting. New SSDs in the market today use power loss protection circuits, wear leveling techniques and thermal throttling to ensure longevity.		HDDs have moving parts, and are subject to potential mechanical failures from the resulting wear and tear so in theory should be less reliable than SSDs. However, in practice this is unclear,
The storage medium itself does not essentially degrade from read and write operations.
According to a study performed by Carnegie Mellon University for both consumer and enterprise-grade HDDs, their average failure rate is 6 years, and life expectancy is 9–11 years. However the risk of a sudden, catastrophic data loss can be lower for HDDs.
When stored offline in long term, the magnetic medium of HDD retains data significantly longer than flash memory used in SSDs.
Start-up timeAlmost instantaneous; no mechanical components to prepare. May need a few milliseconds to come out of an automatic power-saving mode.Drive spin-up may take several seconds. A system with many drives may need to stagger spin-up to limit peak power drawn, which is briefly high when an HDD is first started.
Sequential access performanceIn consumer products the maximum transfer rate typically ranges from about 200 MB/s to 3500 MB/s, depending on the drive. Enterprise SSDs can have multi-gigabyte per second throughput.Once the head is positioned, when reading or writing a continuous track, a modern HDD can transfer data at about 200 MB/s. Data transfer rate depends also upon rotational speed, which can range from 3,600 to 15,000 rpm and also upon the track. Data transfer speed can be up to 480 MB/s.
Random access performanceRandom access time typically under 0.1 ms. As data can be retrieved directly from various locations of the flash memory, access time is usually not a big performance bottleneck. Read performance does not change based on where data is stored. In applications, where hard disk drive seeks are the limiting factor, this results in faster boot and application launch times.
SSD technology can deliver rather consistent read/write speed, but when lots of individual smaller blocks are accessed, performance is reduced.
Flash memory must be erased before it can be rewritten to. This requires an excess number of write operations over and above that intended, which negatively impacts performance.		Read latency time is much higher than SSDs. Random access time ranges from 2.9 to 12 ms due to the need to move the heads and wait for the data to rotate under the magnetic head. Read time is different for every different seek, since the location of the data and the location of the head are likely different. If data from different areas of the platter must be accessed, as with fragmented files, response times will be increased by the need to seek each fragment.
Impact of file system fragmentationThere is limited benefit to reading data sequentially, making fragmentation negligible for SSDs. Defragmentation would cause wear by making additional writes of the NAND flash cells, which have a limited cycle life. However, even with SSDs there is a practical limit on how much fragmentation certain file systems can sustain; once that limit is reached, subsequent file allocations fail. Consequently, defragmentation may still be necessary, although to a lesser degree.Some file systems, like NTFS, become fragmented over time if frequently written; periodic defragmentation is required to maintain optimum performance.
Noise SSDs have no moving parts and therefore are silent, although, on some SSDs, high pitch noise from the high voltage generator may occur.HDDs have moving parts and make characteristic sounds of whirring and clicking; noise levels vary depending on the RPM, but can be significant. Laptop hard drives are relatively quiet.
Temperature controlA Facebook study found that at operating temperatures above 40 °C, the failure rate among SSDs increases with temperature. However, this was not the case with newer drives that employ thermal throttling, albeit at a potential cost to performance. In practice, SSDs usually do not require any special cooling and can tolerate higher temperatures than HDDs. High-end enterprise models installed as add-on cards or 2.5-inch bay devices may ship with heat sinks to dissipate generated heat, requiring certain volumes of airflow to operate.Ambient temperatures above can shorten the life of a hard disk, and reliability will be compromised at drive temperatures above. Fan cooling may be required if temperatures would otherwise exceed these values. In practice, modern HDDs may be used with no special arrangements for cooling.
Lowest operating temperatureSSDs can operate at.Most modern HDDs can operate at.
Highest altitude when operatingSSDs have no issues on this.HDDs can operate safely at an altitude of at most 3,000 meters. HDDs will fail to operate at altitudes above 12,000 meters. With the introduction of helium-filled HDDs, this is expected to be less of an issue.
Moving from a cold environment to a warmer environmentSSDs have no issues on this.A certain amount of acclimation time is needed when moving HDDs from a cold environment to a warmer environment before operating it; otherwise, internal condensation will occur and operating it immediately will result in damage to its internal components.
Breather holeSSDs do not require a breather hole.Most modern HDDs require a breather hole in order to function properly. Helium-filled devices are sealed and do not have a hole.
Susceptibility to environmental factorsNo moving parts, very resistant to shock, vibration, movement, and contamination.Heads flying above rapidly rotating platters are susceptible to shock, vibration, movement, and contamination which could damage the medium.
Installation and mountingNot sensitive to orientation, vibration, or shock. Usually no exposed circuitry. Circuitry may be exposed in a card form device and it must not be short-circuited by conductive materials.Circuitry may be exposed, and it must not be short-circuited by conductive materials. Should be mounted to protect against vibration and shock. Some HDDs should not be installed in a tilted position.
Susceptibility to magnetic fieldsLow impact on flash memory, but an electromagnetic pulse will damage any electrical system, especially integrated circuits.In general, magnets or magnetic surges may result in data corruption or mechanical damage to the drive internals. Drive's metal case provides a low level of shielding to the magnetic platters.
Weight and sizeSSDs, essentially semiconductor memory devices mounted on a circuit board, are small and lightweight. They often follow the same form factors as HDDs or are bare PCBs The enclosures on most mainstream models, if any, are made mostly of plastic or lightweight metal. High performance models often have heatsinks attached to the device, or have bulky cases that serves as its heatsink, increasing its weight.HDDs are generally heavier than SSDs, as the enclosures are made mostly of metal, and they contain heavy objects such as motors and large magnets. 3.5-inch drives typically weigh around 700 grams.
Secure writing limitationsNAND flash memory cannot be overwritten, but has to be rewritten to previously erased blocks. If a software encryption program encrypts data already on the SSD, the overwritten data is still unsecured, unencrypted, and accessible. Also data cannot be securely erased by overwriting the original file without special "Secure Erase" procedures built into the drive.HDDs can overwrite data directly on the drive in any particular sector. However, the drive's firmware may exchange damaged blocks with spare areas, so bits and pieces may still be present. Some manufacturers' HDDs fill the entire drive with zeroes, including relocated sectors, on ATA Secure Erase Enhanced Erase command.
Read/write performance symmetryLess expensive SSDs typically have write speeds significantly lower than their read speeds. Higher performing SSDs have similar read and write speeds.HDDs generally have slightly longer seek times for writing than for reading.
Free block availability and TRIMSSD write performance is significantly impacted by the availability of free, programmable blocks. Previously written data blocks no longer in use can be reclaimed by TRIM; however, even with TRIM, fewer free blocks cause slower performance.HDDs are not affected by free blocks and do not benefit from TRIM.
Power consumptionHigh performance flash-based SSDs generally require half to a third of the power of HDDs. High-performance DRAM SSDs generally require as much power as HDDs, and must be connected to power even when the rest of the system is shut down. Emerging technologies like DevSlp can minimize power requirements of idle drives.The lowest-power HDDs can use as little as 0.35 watts when idle. 2.5-inch drives typically use 2 to 5 watts. The highest-performance 3.5-inch drives can use up to about 20 watts.
Maximum areal storage density 2.81.2

Memory cards

While both memory cards and most SSDs use flash memory, they serve very different markets and purposes. Each has a number of different attributes which are optimized and adjusted to best meet the needs of particular users. Some of these characteristics include power consumption, performance, size, and reliability.
SSDs were originally designed for use in a computer system. The first units were intended to replace or augment hard disk drives, so the operating system recognized them as a hard drive. Originally, solid state drives were even shaped and mounted in the computer like hard drives. Later SSDs became smaller and more compact, eventually developing their own unique form factors such as the M.2 form factor. The SSD was designed to be installed permanently inside a computer.
In contrast, memory cards, CompactFlash were originally designed for digital cameras and later found their way into cell phones, gaming devices, GPS units, etc. Most memory cards are physically smaller than SSDs, and designed to be inserted and removed repeatedly. There are adapters which enable some memory cards to interface to a computer, allowing use as an SSD, but they are not intended to be the primary storage device in the computer. The typical CompactFlash card interface is three to four times slower than an SSD. As memory cards are not designed to tolerate the amount of reading and writing which occurs during typical computer use, their data may get damaged unless special procedures are taken to reduce the wear on the card to a minimum.

SSD failure

SSDs have very different failure modes from traditional magnetic hard drives. Because of their design, some kinds of failure are inapplicable. Instead, other kinds of failure are possible. However, on the whole statistics show that SSDs are generally highly reliable, and often continue working far beyond the expected lifetime as stated by their manufacturer.
The endurance of an SSD should be provided on its datasheet in one of two forms:
So for example a Samsung 970 EVO NVMe M.2 SSD with 1 TB has an endurance of 600 TBW.

SSD reliability and failure modes

An early investigation by Techreport.com that ran from 2013 to 2015 involved a number of flash-based SSDs being tested to destruction to identify how and at what point they failed. The website found that all of the drives "surpassed their official endurance specifications by writing hundreds of terabytes without issue"—volumes of that order being in excess of typical consumer needs. The first SSD to fail was TLC-based, with the drive succeeding in writing over 800,000 GB. Three SSDs in the test wrote three times that amount before they too failed. The test demonstrated the remarkable reliability of even consumer-market SSDs.
A 2016 field study based on data collected over six years in Google's data centre and spanning "millions" of drive days found that the proportion of flash-based SSDs requiring replacement in their first four years of use ranged from 4% to 10% depending on the model. The authors concluded that SSDs fail at a significantly lower rate than hard disk drives. The study also showed, on the down-side, that SSDs experience significantly higher rates of uncorrectable errors than do HDDs. It also led to some unexpected results and implications:
Solid state drives have set new challenges for data recovery companies, as the way of storing data is non-linear and much more complex than that of hard disk drives. The strategy by which the drive operates internally can vary largely between manufacturers, and the TRIM command zeroes the whole range of a deleted file. Wear leveling also means that the physical address of the data and the address exposed to the operating system are different.
As for secure deletion of data, ATA Secure Erase command could be used. A program such as hdparm can be used for this purpose.

Reliability metrics

The JEDEC Solid State Technology Association has published standards for reliability metrics:
Due to their generally prohibitive cost versus HDDs at the time, until 2009, SSDs were mainly used in those aspects of mission critical applications where the speed of the storage system needed to be as high as possible. Since flash memory has become a common component of SSDs, the falling prices and increased densities have made it more cost-effective for many other applications. For instance, in the distributed computing environment, SSDs can be used as the building block for a distributed cache layer that temporarily absorbs the large volume of user requests to the slower HDD based backend storage system. This layer provides much higher bandwidth and lower latency than the storage system, and can be managed in a number of forms, such as distributed key-value database and distributed file system. On the supercomputers, this layer is typically referred to as burst buffer. With this fast layer, users often experience shorter system response time. Organizations that can benefit from faster access of system data include equity trading companies, telecommunication corporations, and streaming media and video editing firms. The list of applications which could benefit from faster storage is vast.
Flash-based solid-state drives can be used to create network appliances from general-purpose personal computer hardware. A write protected flash drive containing the operating system and application software can substitute for larger, less reliable disk drives or CD-ROMs. Appliances built this way can provide an inexpensive alternative to expensive router and firewall hardware.
SSDs based on an SD card with a live SD operating system are easily write-locked. Combined with a cloud computing environment or other writable medium, to maintain persistence, an OS booted from a write-locked SD card is robust, rugged, reliable, and impervious to permanent corruption. If the running OS degrades, simply turning the machine off and then on returns it back to its initial uncorrupted state and thus is particularly solid. The SD card installed OS does not require removal of corrupted components since it was write-locked though any written media may need to be restored.

Hard drives caching

In 2011, Intel introduced a caching mechanism for their Z68 chipset called Smart Response Technology, which allows a SATA SSD to be used as a cache for a conventional, magnetic hard disk drive. A similar technology is available on HighPoint's RocketHybrid PCIe card.
Solid-state hybrid drives are based on the same principle, but integrate some amount of flash memory on board of a conventional drive instead of using a separate SSD. The flash layer in these drives can be accessed independently from the magnetic storage by the host using ATA-8 commands, allowing the operating system to manage it. For example, Microsoft's ReadyDrive technology explicitly stores portions of the hibernation file in the cache of these drives when the system hibernates, making the subsequent resume faster.
Dual-drive hybrid systems are combining the usage of separate SSD and HDD devices installed in the same computer, with overall performance optimization managed by the computer user, or by the computer's operating system software. Examples of this type of system are bcache and dm-cache on Linux, and Apple's Fusion Drive.

File system support for SSDs

Typically the same file systems used on hard disk drives can also be used on solid state drives. It is usually expected for the file system to support the TRIM command which helps the SSD to recycle discarded data. This means that file system does not need to manage wear leveling or other flash memory characteristics, as they are handled internally by the SSD. Some flash file systems using log-based designs help to reduce write amplification on SSDs, especially in situations where only very small amounts of data are changed, such as when updating file-system metadata.
While not a file system feature, operating systems should also aim to align partitions correctly, which avoids excessive read-modify-write cycles. A typical practice for personal computers is to have each partition aligned to start at a 1 MiB mark, which covers all common SSD page and block size scenarios, as it is divisible by all commonly used sizes - 1 MiB, 512 KiB, 128 KiB, 4 KiB, and 512 B. Modern operating system installation software and disk tools handle this automatically.

Linux

The ext4, Btrfs, XFS, JFS, and F2FS file systems include support for the discard function.
Kernel support for the TRIM operation was introduced in version 2.6.33 of the Linux kernel mainline, released on. To make use of it, a file system must be mounted using the discard parameter. Linux swap partitions are by default performing discard operations when the underlying drive supports TRIM, with the possibility to turn them off, or to select between one-time or continuous discard operations. Support for queued TRIM, which is a SATA 3.1 feature that results in TRIM commands not disrupting the command queues, was introduced in Linux kernel 3.12, released on November 2, 2013.
An alternative to the kernel-level TRIM operation is to use a user-space utility called that goes through all of the unused blocks in a filesystem and dispatches TRIM commands for those areas. utility is usually run by cron as a scheduled task., it is used by the Ubuntu Linux distribution, in which it is enabled only for Intel and Samsung solid-state drives for reliability reasons; vendor check can be disabled by editing file using instructions contained within the file itself.
Since 2010, standard Linux drive utilities have taken care of appropriate partition alignment by default.

Linux performance considerations

During installation, Linux distributions usually do not configure the installed system to use TRIM and thus the /etc/fstab file requires manual modifications. This is because of the notion that the current Linux TRIM command implementation might not be optimal. It has been proven to cause a performance degradation instead of a performance increase under certain circumstances., Linux sends an individual TRIM command to each sector, instead of a vectorized list defining a TRIM range as recommended by the TRIM specification. This deficiency has existed for years and there are no known plans to eliminate it.
For performance reasons, it is recommended to switch the I/O scheduler from the default CFQ to NOOP or Deadline. CFQ was designed for traditional magnetic media and seek optimizations, thus many of those I/O scheduling efforts are wasted when used with SSDs. As part of their designs, SSDs offer much bigger levels of parallelism for I/O operations, so it is preferable to leave scheduling decisions to their internal logic especially for high-end SSDs.
A scalable block layer for high-performance SSD storage, known as blk-multiqueue or blk-mq and developed primarily by Fusion-io engineers, was merged into the Linux kernel mainline in kernel version 3.13, released on 19 January 2014. This leverages the performance offered by SSDs and NVM Express, by allowing much higher I/O submission rates. With this new design of the Linux kernel block layer, internal queues are split into two levels, thus removing bottlenecks and allowing much higher levels of I/O parallelization. As of version 4.0 of the Linux kernel, released on 12 April 2015, VirtIO block driver, the SCSI layer, device mapper framework, loop device driver, unsorted block images driver and RBD driver have been modified to actually use this new interface; other drivers will be ported in the following releases.

macOS

Versions since Mac OS X 10.6.8 support TRIM but only when used with an Apple-purchased SSD. TRIM is not automatically enabled for third-party drives, although it can be enabled by using third-party utilities such as Trim Enabler. The status of TRIM can be checked in the System Information application or in the system_profiler command-line tool.
Versions since OS X 10.10.4 include sudo trimforce enable as a Terminal command that enables TRIM on non-Apple SSDs. There is also a technique to enable TRIM in versions earlier than Mac OS X 10.6.8, although it remains uncertain whether TRIM is actually utilized properly in those cases.

Microsoft Windows

Prior to version 7, Microsoft Windows did not take any specific measures to support solid state drives. From Windows 7, the standard NTFS file system provides support for the TRIM command.
By default, Windows 7 and newer versions execute TRIM commands automatically if the device is detected to be a solid-state drive. However, because TRIM irreversibly resets all freed space, it may be desirable to disable support where enabling data recovery is preferred over wear leveling. To change the behavior, in the Registry key the value can be set to. This prevents the mass storage driver issuing the TRIM command.
Windows implements TRIM command for more than just file-delete operations. The TRIM operation is fully integrated with partition- and volume-level commands such as format and delete, with file system commands relating to truncate and compression, and with the System Restore feature.

Windows Vista

generally expects hard disk drives rather than SSDs. Windows Vista includes ReadyBoost to exploit characteristics of USB-connected flash devices, but for SSDs it only improves the default partition alignment to prevent read-modify-write operations that reduce the speed of SSDs. Most SSDs are typically split into 4 KiB sectors, while most systems are based on 512 byte sectors with their default partition setups unaligned to the 4 KiB boundaries. The proper alignment does not help the SSD's endurance over the life of the drive; however, some Vista operations, if not disabled, can shorten the life of the SSD.
Drive defragmentation should be disabled because the location of the file components on an SSD doesn't significantly impact its performance, but moving the files to make them contiguous using the Windows Defrag routine will cause unnecessary write wear on the limited number of P/E cycles on the SSD. The Superfetch feature will not materially improve the performance of the system and causes additional overhead in the system and SSD, although it does not cause wear. Windows Vista does not send the TRIM command to solid state drives, but some third part utilities such as SSD Doctor will periodically scan the drive and TRIM the appropriate entries.

Windows 7

Windows 7 and later versions have native support for SSDs. The operating system detects the presence of an SSD and optimizes operation accordingly. For SSD devices Windows disables SuperFetch and ReadyBoost, boot-time and application prefetching operations. Despite the initial statement by Steven Sinofsky before the release of Windows 7, however, defragmentation is not disabled, even though its behavior on SSDs differs. One reason is the low performance of Volume Shadow Copy Service on fragmented SSDs. The second reason is to avoid reaching the practical maximum number of file fragments that a volume can handle. If this maximum is reached, subsequent attempts to write to the drive will fail with an error message.
Windows 7 also includes support for the TRIM command to reduce garbage collection for data which the operating system has already determined is no longer valid. Without support for TRIM, the SSD would be unaware of this data being invalid and would unnecessarily continue to rewrite it during garbage collection causing further wear on the SSD. It is beneficial to make some changes that prevent SSDs from being treated more like HDDs, for example cancelling defragmentation, not filling them to more than about 75% of capacity, not storing frequently written-to files such as log and temporary files on them if a hard drive is available, and enabling the TRIM process.

Windows 8.1

Windows 8.1 and later Windows systems like Windows 10 also support automatic TRIM for PCI Express SSDs based on NVMe. For Windows 7, the KB2990941 update is required for this functionality and needs to be integrated into Windows Setup using DISM if Windows 7 has to be installed on the NVMe SSD. Windows 8/8.1 also support the SCSI unmap command for USB-attached SSDs or SATA-to-USB enclosures. SCSI Unmap is a full analog of the SATA TRIM command. It is also supported over USB Attached SCSI Protocol.
The graphical Windows Disk Defagmenter in Windows 8.1 also recognizes SSDs distinctly from hard disk drives in a separate Media Type column. While Windows 7 supported automatic TRIM for internal SATA SSDs, Windows 8.1 and Windows 10 support manual TRIM as well as automatic TRIM for SATA, NVMe and USB-attached SSDs.

ZFS

as of version 10 Update 6, and recent versions of OpenSolaris, Solaris Express Community Edition, Illumos, Linux with ZFS on Linux, and FreeBSD all can use SSDs as a performance booster for ZFS. A low-latency SSD can be used for the ZFS Intent Log, where it is named the SLOG. This is used every time a synchronous write to the drive occurs. An SSD may also be used for the level 2 Adaptive Replacement Cache, which is used to cache data for reading. When used either alone or in combination, large increases in performance are generally seen.

FreeBSD

ZFS for FreeBSD introduced support for TRIM on September 23, 2012. The code builds a map of regions of data that were freed; on every write the code consults the map and eventually removes ranges that were freed before, but are now overwritten. There is a low-priority thread that TRIMs ranges when the time comes.
Also the Unix File System supports the TRIM command.

Swap partitions

The following are noted standardization organizations and bodies that work to create standards for solid-state drives. The table below also includes organizations which promote the use of solid-state drives. This is not necessarily an exhaustive list.
Organization or committeeSubcommittee of:Purpose
INCITSCoordinates technical standards activity between ANSI in the US and joint ISO/IEC committees worldwide
T10INCITSSCSI
T11INCITSFC
T13INCITSATA
JEDECDevelops open standards and publications for the microelectronics industry
JC-64.8JEDECFocuses on solid-state drive standards and publications
NVMHCIProvides standard software and hardware programming interfaces for nonvolatile memory subsystems
SATA-IOProvides the industry with guidance and support for implementing the SATA specification
SFF CommitteeWorks on storage industry standards needing attention when not addressed by other standards committees
SNIADevelops and promotes standards, technologies, and educational services in the management of information
SSSISNIAFosters the growth and success of solid state storage

Commercialization

Availability

Solid-state drive technology has been marketed to the military and niche industrial markets since the mid-1990s.
Along with the emerging enterprise market, SSDs have been appearing in ultra-mobile PCs and a few lightweight laptop systems, adding significantly to the price of the laptop, depending on the capacity, form factor and transfer speeds. For low-end applications, a USB flash drive may be obtainable for anywhere from $10 to $100 or so, depending on capacity and speed; alternatively, a CompactFlash card may be paired with a CF-to-IDE or CF-to-SATA converter at a similar cost. Either of these requires that write-cycle endurance issues be managed, either by refraining from storing frequently written files on the drive or by using a flash file system. Standard CompactFlash cards usually have write speeds of 7 to 15 MB/s while the more expensive upmarket cards claim speeds of up to 60 MB/s.
The first flash-memory SSD based PC to become available was the Sony Vaio UX90, announced for pre-order on 27 June 2006 and began shipping in Japan on 3 July 2006 with a 16 GB flash memory hard drive. In late September 2006 Sony upgraded the SSD in the Vaio UX90 to 32 GB.
One of the first mainstream releases of SSD was the XO Laptop, built as part of the One Laptop Per Child project. Mass production of these computers, built for children in developing countries, began in December 2007. These machines use 1,024 MiB SLC NAND flash as primary storage which is considered more suitable for the harsher than normal conditions in which they are expected to be used. Dell began shipping ultra-portable laptops with SanDisk SSDs on April 26, 2007. Asus released the Eee PC subnotebook on October 16, 2007, with 2, 4 or 8 gigabytes of flash memory. On January 31, 2008, Apple released the MacBook Air, a thin laptop with an optional 64 GB SSD. The Apple Store cost was $999 more for this option, as compared with that of an 80 GB 4200 RPM hard disk drive. Another option, the Lenovo ThinkPad X300 with a 64 gigabyte SSD, was announced by Lenovo in February 2008. On August 26, 2008, Lenovo released ThinkPad X301 with 128 GB SSD option which adds approximately $200 US.
In 2008, low-end netbooks appeared with SSDs. In 2009, SSDs began to appear in laptops.
On January 14, 2008, EMC Corporation became the first enterprise storage vendor to ship flash-based SSDs into its product portfolio when it announced it had selected STEC, Inc.'s Zeus-IOPS SSDs for its Symmetrix DMX systems. In 2008, Sun released the Sun Storage 7000 Unified Storage Systems, which use both solid state drives and conventional hard drives to take advantage of the speed offered by SSDs and the economy and capacity offered by conventional HDDs.
Dell began to offer optional 256 GB solid state drives on select notebook models in January 2009. In May 2009, Toshiba launched a laptop with a 512 GB SSD.
Since October 2010, Apple's MacBook Air line has used a solid state drive as standard. In December 2010, OCZ RevoDrive X2 PCIe SSD was available in 100 GB to 960 GB capacities delivering speeds over 740 MB/s sequential speeds and random small file writes up to 120,000 IOPS. In November 2010, Fusion-io released its highest performing SSD drive named ioDrive Octal utilising PCI-Express x16 Gen 2.0 interface with storage space of 5.12 TB, read speed of 6.0 GB/s, write speed of 4.4 GB/s and a low latency of 30 microseconds. It has 1.19 M Read 512 byte IOPS and 1.18 M Write 512 byte IOPS.
In 2011, computers based on Intel's Ultrabook specifications became available. These specifications dictate that Ultrabooks use an SSD. These are consumer-level devices, and represent the first widely available consumer computers using SSDs aside from the MacBook Air. At CES 2012, OCZ Technology demonstrated the R4 CloudServ PCIe SSDs capable of reaching transfer speeds of 6.5 GB/s and 1.4 million IOPS. Also announced was the Z-Drive R5 which is available in capacities up to 12 TB, capable of reaching transfer speeds of 7.2 GB/s and 2.52 million IOPS using the PCI Express x16 Gen 3.0.
In December 2013, Samsung introduced and launched the industry's first 1 TB mSATA SSD. In August 2015, Samsung announced a 16 TB SSD, at the time the world's highest-capacity single storage device of any type.
While a number of companies offer SSD devices as of 2018 only five of the companies that offer them actually manufacture the Nand Flash devices that are the storage element in SSDs.

Quality and performance

In general, performance of any particular device can vary significantly in different operating conditions. For example, the number of parallel threads accessing the storage device, the I/O block size, and the amount of free space remaining can all dramatically change the performance of the device.
SSD technology has been developing rapidly. Most of the performance measurements used on disk drives with rotating media are also used on SSDs. Performance of flash-based SSDs is difficult to benchmark because of the wide range of possible conditions. In a test performed in 2010 by Xssist, using IOmeter, 4 kB random 70% read/30% write, queue depth 4, the IOPS delivered by the Intel X25-E 64 GB G1 started around 10,000 IOPs, and dropped sharply after 8 minutes to 4,000 IOPS, and continued to decrease gradually for the next 42 minutes. IOPS vary between 3,000 and 4,000 from around 50 minutes onwards for the rest of the 8+ hour test run.
Designers of enterprise-grade flash drives try to extend longevity by increasing over-provisioning and by employing wear leveling.

Sales

SSD shipments were 11 million units in 2009, 17.3 million units in 2011 for a total of US$5 billion, 39 million units in 2012, and were expected to rise to 83 million units in 2013
to 201.4 million units in 2016 and to 227 million units in 2017.
Revenues for the SSD market worldwide totalled $585 million in 2008, rising over 100% from $259 million in 2007.