[Lustre-discuss] Multi-Role/Tasking MDS/OSS Hosts

[Brian J. Murrell]

On Fri, 2010-09-17 at 10:42 -0800, Jonathan B. Horen wrote: 
> 
> Background: Our OSTs

OSSes.  OSTs are the disks that an OSS provides object service with.

> Primary MDS would be a 72-cpu IBM x3950m2, which would
> also be an OSS.

MDS and OSS on the same node is an unsupported configuration due to the
fact that if it fails you will have a "double failure" and recovery
cannot be performed.

> Secondary MDS would be a 2-cpu Penguin Computing Altus-1300,
> which would also be an OSS.

Ditto.

> Are there basic conflicts-of-interest, and/or known/potential "gotchas" in
> utilizing hosts in such multi-purpose roles? 

OSSes and MDSes require a kernel patched for Lustre.  So you'd need to
be able to either replace the kernel on those existing machines or patch
the source you built it from.

Generally speaking, you are of course going to have only as much
performance as the Lustre services on those shared nodes will be able to
get the resources it wants.  Our usual recommendation is to dedicate OSS
and MDS nodes for this reason, but there is no hard rule that you must
provide dedicated nodes, so long as everything else on the nodes can
live with the patched Lustre kernel.  If you are already patching those
kernels for something else, you could run into conflicts trying to patch
them for Lustre.

b.

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