Volunteer computing is a type of distributed computing in which people donate their computers' unused resources to a research-oriented project. The practice, which dates back to the mid-1990s, can potentially make substantial processing power available to researchers at minimal cost. Typically, a program running on a volunteer's computer periodically contacts a research application to request jobs and report results. A middleware system usually serves as an intermediary.
The client software of the early volunteer computing projects consisted of a single program that combined the scientific computation and the distributed computing infrastructure. This monolithic architecture was inflexible. For example, it was difficult to deploy new application versions. More recently, volunteer computing has moved to middleware systems that provide a distributed computing infrastructure independent from the scientific computation. Examples include:
The Berkeley Open Infrastructure for Network Computing is the most widely used middleware system. It offers client software for Windows, Mac OS X, Linux, Android, and other Unix variants.
XtremWeb is used primarily as a research tool. It is developed by a group based at the University of Paris-South.
Xgrid is developed by Apple. Its client and server components run only on Mac OS X.
Grid MP is a commercial middleware platform developed by United Devices and was used in volunteer computing projects including grid.org, World Community Grid, Cell Computing, and Hikari Grid.
Most of these systems have the same basic structure: a client program runs on the volunteer's computer. It periodically contacts project-operated servers over the Internet, requesting jobs and reporting the results of completed jobs. This "pull" model is necessary because many volunteer computers are behind firewalls that do not allow incoming connections. The system keeps track of each user's "credit", a numerical measure of how much work that user's computers have done for the project. Volunteer computing systems must deal with several issues involving volunteered computers: their heterogeneity, their churn, their sporadic availability, and the need to not interfere with their performance during regular use. In addition, volunteer computing systems must deal with problems related to correctness:
Volunteers are unaccountable and essentially anonymous.
Some volunteer computers occasionally malfunction and return incorrect results.
Some volunteers intentionally return incorrect results or claim excessive credit for results.
One common approach to these problems is replicated computing, in which each job is performed on at least two computers. The results are accepted only if they agree sufficiently.
Drawbacks for participants
Increased power consumption: A CPU generally uses more electricity when it is active compared to when it is idle. Additionally, the desire to participate may cause the volunteer to leave the PC on overnight or disable power-saving features like suspend. Furthermore, if the computer cannot cool itself adequately, the added load on the volunteer's CPU can cause it to overheat.
Decreased performance of the PC: If the volunteer computing application runs while the computer is in use, it may impact performance of the PC. This is due to increased usage of the CPU, CPU cache, local storage, and network connection. If RAM is a limitation, increased disk cache misses and/or increased paging can result. Volunteer computing applications typically execute at a lower CPU scheduling priority, which helps to alleviate CPU contention.
These effects may or may not be noticeable, and even if they are noticeable, the volunteer might choose to continue participating. However, the increased power consumption can be remedied to some extent by setting an option to limit the percentage of the processor used by the client, which is available in some client software.
Benefits for researchers
Volunteer computing can provide researchers with computing power that is not achievable any other way. Approximately 10 petaflops of computing power are available from volunteer computing networks.
Volunteer computing is often cheaper than other forms of distributed computing.
Importance
Although there are issues such as lack of accountability and trust between participants and researchers while implementing the projects, volunteer computing is crucially important, especially to projects that have limited funding.
Since there are more than one billion PCs in the world, volunteer computing can supply more computing power to researches, that do not have the required competencies regarding the computing power, on any kind of topic; such as academic or scientific researches. Also, advancements in the technology will provide the advancements in consumer products such as PCs and game consoles happen faster than any other specialized products which will increase the number of PCs and computing power in the world consequently.
Supercomputers that have huge computing power are extremely expensive and are available only to some applications only if they can afford it. Whereas volunteer computing is not something that can be bought, its power arises from the public support. A research project that has limited sources and funding can get huge computing power by attracting public attention.
By volunteering and providing support and computing power to the researches on topics such as science, citizens are encouraged to be interested in science and also citizens are allowed to have a voice in directions of scientific researches and eventually the future science by providing support or not to the researches.
