[Beowulf] Mosix

[John Hearns]

> Hi,
>
> I am newbee to cluster computing; so if my question sounds stupid, please
> excuse me.
>
> i am wondering when we have something like mosix (distributed OS available
> at www.mosix.org ), why we should still develop parallel programs and
> strugle with PVM/MPI etc. Tough i never used either mosix or PVM/MPI, I am
> genunely puzzled about it. Can someone kindly educate me?
>
Rajesh,
   I apologise for a short answer, but I am busy right at the moment!

Mosix deals with process migration. A compute-intensive process is stopped,
and checkpointed, on the master node of the cluster. It is then transferred
and restarted on one of the cluster nodes.
So Mosix is good for the situation where you have programs which use a lot
of CPU resource on one machine. For the process to transfer, all the
machines must be running the same kernel version.

PVM/MPI are parallel programming libraries.
You can run MPI programs on different types of machines - the intent was
that parallel codes could be ported from (say) Crays to IBM machines.
If you want to run programs which can split their computation between lots
and lots of CPUs then MPI is a good choice.
For instance, I am at the moment preparing a system which has over 500
dual-CPU systems to run a big benchmark.
MOSIX would not be suitable for getting that number of parallel processes
up, running and comunicating.

I should make clear that MOSIX has its place - making it simple and easy to
run compute intensive jobs, say perhaps bioinformatics searches, codes
which do not need inter-node communication.

Hope others will add/correct my reply.

John Hearns