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Nowadays, volunteer computing (VoC) and grid computing are well-established paradigms of distributed computing. The term “volunteer computing” is used for all scenarios where a low priority guest application can run on unused remote resources without significantly impacting high priority host applications (Vyas & Subhlok, 2007). In other words, in volunteer computing, individuals donate unused or idle resources of their computers to distributed computing applications.
On the other hand, Grid computing combines computing resources from multiple administrative domains, using open standards to achieve non-trivial quality of service (Foster, 2002), often in order to provide improved performance, availability or throughput for applications.
Here, we call Grid and VoC platforms generically middlewares, but there are several characteristics that distinguish the volunteer computing from Grid (Anderson, 2007), namely:
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The number of volunteer nodes in VoC systems may range from less than 10 to hundreds of thousands.
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Volunteered resources are owned and managed by regular people, not by IT professionals
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Volunteers are anonymous, and those who misbehave cannot be fired or prosecuted.
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Volunteered resources are often behind network firewalls that do not allow incoming connections. This requires the use of a “pull” model rather than the “push” model used by most grid computing software.
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Volunteer computing is asymmetric: volunteers supply resources, and not the other way round. Grid computing, in contrast, is symmetric: an organization can borrow resources one day and supply them the next.
The best known Grid systems are gLite (Laure et al., 2006), Advanced Resource Connector (ARC) (Ellert et al., 2007), Globus (Foster & Kesselman, 1997), Unicore (Erwin & Snelling, 2001), Condor-G (Frey, Tannenbaum, & Livny, 2002), and GridMP.
The Berkeley Open Infrastructure for Network Computing (BOINC) (Anderson, 2004) is the most widely used middleware in volunteer computing. Like BOINC, XtremWeb (XW) (Cappello et al., 2004) is a VoC middleware providing a framework and a set of tools to assist in the creation of volunteer computing projects.
XtremWeb-CH (XWCH:http://bilbo.iut-bm.univ-fcomte.fr/fromP2P). One of the main objectives of these two projects is to deploy scientific medical applications. Three applications are being gridified within these projects, but for the sake of brevity we only discuss two of them.