I think there are two questions here: 1. Running MPI applications on "slow" networks (e.g., 100mbps). This is very much application-dependent. If your MPI app doesn't communication with other processes much, then it probably won't matter. If you have latency/bandwidth-sensitive applications, then using a "slow" network can definitely have a negative impact on performance.
2. Running MPI applications on resources that are being used by others. In this case, your MPI processes will be competing with other processes for CPU, RAM, and other resources -- just like any other process. Hence, your overall performance will depend not only on the application, but also on the usage patterns of the other resources (e.g., the workstations and the people that use them). I have certainly heard of bunches of success stories in this kind of environment -- small numbers of relatively lightly-loaded workstations (typically <= 16) running small to mid-sized MPI applications, etc. A common case for such scenarios is for development and debugging, or even running small versions of jobs when you can't get time on larger resources, etc. Specifically: sometimes running a smaller version of your job is better than not running anything at all. Hope that helps. On 7/20/06 10:04 AM, "Brock Palen" <bro...@umich.edu> wrote: > Its doable, the scaling will not as good, because a network is a > network. If you are using just regular 100Mbit, you will not scale > as far as really good 1gig ethernet, but we are still talking about > tcp which incurs a penalty over networks like infiniband and myrinet. > Tcp is the largest issue, its going to be really application > dependent you are right. > On another note though many of the older cluster that are now out of > service used just 100Mbit ethernet and worked. > > Brock Palen > Center for Advanced Computing > bro...@umich.edu > (734)936-1985 > > > On Jul 20, 2006, at 9:27 AM, Vladimir Sipos wrote: > >> Hi, >> >> Is MPI paradigm applicable to the cluster of regular networked >> machines. >> That is, does the cost of network IO offset benefits of >> parallelization? >> My guess is that this really depends on the application itself, >> however, >> I'm wondering if you guys know of any success stories which involve >> MPI >> running on a set of networked machines (not beowulf cluster or any >> SC). >> >> Thanks, >> >> Vladimir Sipos >> Software Engineer >> Advertising Technology >> CNET Networks, Inc. >> >> >> >> >> >> _______________________________________________ >> users mailing list >> us...@open-mpi.org >> http://www.open-mpi.org/mailman/listinfo.cgi/users >> >> > > _______________________________________________ > users mailing list > us...@open-mpi.org > http://www.open-mpi.org/mailman/listinfo.cgi/users -- Jeff Squyres Server Virtualization Business Unit Cisco Systems
