[Beowulf] Similar to a multi CPU machine?

Tony Travis ajt at rri.sari.ac.uk
Mon Nov 14 09:06:19 EST 2005

Robert G. Brown wrote:
> On Wed, 9 Nov 2005, Jake Thebault-Spieker wrote:
>> Is there a way to make a cluster act like a dual(or triple, quad, 
>> etc.) CPU
>> machine? I'vee been looking at purchasing a dual PII machine, but then
>> realized that I have six 166Mhz machines sitting around doing nothing. 
>> Does
>> OpenMosix do this? Is there OpenMosix for 2.6.x? This will be run on 
>> debian,
>> if it works.
> Boy did YOU come to the right list.

Jake could also have a look at:


There is a development version of openMosix for the 2.6 kernel, but most 
'production' clusters are running 2.4 kernels. The openMosix kernel does 
do similar process migration to that done by an SMP kernel, but it does 
it using a network interconnect between CPU's on different machines.

> That is what this list is devoted to, as it has been for coming up on a
> decade now (hey Don, when IS the ten year list anniversary?:-)
> OpenMosix is one solution.  Scyld is another.  bproc (close kin to 
> scyld) is
> a third.

One more possibility is OpenSSI:


This differs from openMosix in that entire processes are migrated 
between machines. OpenMosix only migrates the active pages of the user 
context of processes between machines. It also uses the openMosix 
load-balancing algorithm.

> SGE (or other batch/queue managers) yet another.  Even plain
> old linux and some job management scripts are more than adequate for a
> lot of tasks.

True, and these can also be combined with openMosix to make a very 
flexible and powerful solution to solving a wide range of problems.

> Finally, if you are looking for "true parallel" operation
> (many CPUs working on a single task vs many CPUs working on many tasks)
> there are a whole lot of alternatives involving the distro of your
> choice with e.g. PVM or MPI or raw socket programming layered on top.

That's right - Although openMosix is good at load-balancing you will 
need PVM/MPI to pool the CPU resources of your six PC's. This would be 
the same for an SMP kernel too: However some 'embarassingly' parallel 
tasks do run very well under openMosix, and openMosix can also assist 
the performance of "true parallel" PVM/MPI applications by migrating 
PVM/MPI sub-processes to less heavily burdened CPU's. OpenMosix works at 
kernel level 'below' the PVM/MPI libraries and transparently migrates 
PVM/MPI processes between CPU's on different PC's to balance the load.

> Be careful -- some of these cost money, some of these require a custom
> kernel.

Indeed :-)

Jake, you can try out openMosix without installing it using the 
ClusterKnoppix 'live' CD:


Best wishes,

Dr. A.J.Travis,                     |  mailto:ajt at rri.sari.ac.uk
Rowett Research Institute,          |    http://www.rri.sari.ac.uk/~ajt
Greenburn Road, Bucksburn,          |   phone:+44 (0)1224 712751
Aberdeen AB21 9SB, Scotland, UK.    |     fax:+44 (0)1224 716687
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