Thanks very much, exactly what I wanted to hear. How big is /tmp?
-----Original Message-----
From: users-boun...@open-mpi.org
[mailto:users-boun...@open-mpi.org] On
Behalf Of David Turner
Sent: Thursday, November 03, 2011 6:36 PM
To: us...@open-mpi.org
Subject: Re: [OMPI users] EXTERNAL: Re: How to set up state-less
node /tmp
for OpenMPI usage
I'm not a systems guy, but I'll pitch in anyway. On our cluster,
all the compute nodes are completely diskless. The root file system,
including /tmp, resides in memory (ramdisk). OpenMPI puts these
session directories therein. All our jobs run through a batch
system (torque). At the conclusion of each batch job, an epilogue
process runs that removes all files belonging to the owner of the
current batch job from /tmp (and also looks for and kills orphan
processes belonging to the user). This epilogue had to written
by our systems staff.
I believe this is a fairly common configuration for diskless
clusters.
On 11/3/11 4:09 PM, Blosch, Edwin L wrote:
Thanks for the help. A couple follow-up-questions, maybe this
starts to
go outside OpenMPI:
What's wrong with using /dev/shm? I think you said earlier in
this thread
that this was not a safe place.
If the NFS-mount point is moved from /tmp to /work, would a /tmp
magically
appear in the filesystem for a stateless node? How big would it
be, given
that there is no local disk, right? That may be something I have
to ask the
vendor, which I've tried, but they don't quite seem to get the
question.
Thanks
-----Original Message-----
From: users-boun...@open-mpi.org
[mailto:users-boun...@open-mpi.org] On
Behalf Of Ralph Castain
Sent: Thursday, November 03, 2011 5:22 PM
To: Open MPI Users
Subject: Re: [OMPI users] EXTERNAL: Re: How to set up state-less
node /tmp
for OpenMPI usage
On Nov 3, 2011, at 2:55 PM, Blosch, Edwin L wrote:
I might be missing something here. Is there a side-effect or
performance
loss if you don't use the sm btl? Why would it exist if there is a
wholly
equivalent alternative? What happens to traffic that is intended for
another process on the same node?
There is a definite performance impact, and we wouldn't recommend
doing
what Eugene suggested if you care about performance.
The correct solution here is get your sys admin to make /tmp
local. Making
/tmp NFS mounted across multiple nodes is a major "faux pas" in the
Linux
world - it should never be done, for the reasons stated by Jeff.
Thanks
-----Original Message-----
From: users-boun...@open-mpi.org
[mailto:users-boun...@open-mpi.org] On
Behalf Of Eugene Loh
Sent: Thursday, November 03, 2011 1:23 PM
To: us...@open-mpi.org
Subject: Re: [OMPI users] EXTERNAL: Re: How to set up state-less
node
/tmp for OpenMPI usage
Right. Actually "--mca btl ^sm". (Was missing "btl".)
On 11/3/2011 11:19 AM, Blosch, Edwin L wrote:
I don't tell OpenMPI what BTLs to use. The default uses sm and
puts a
session file on /tmp, which is NFS-mounted and thus not a good choice.
Are you suggesting something like --mca ^sm?
-----Original Message-----
From: users-boun...@open-mpi.org
[mailto:users-boun...@open-mpi.org] On
Behalf Of Eugene Loh
Sent: Thursday, November 03, 2011 12:54 PM
To: us...@open-mpi.org
Subject: Re: [OMPI users] EXTERNAL: Re: How to set up state-less
node
/tmp for OpenMPI usage
I've not been following closely. Why must one use shared-memory
communications? How about using other BTLs in a "loopback"
fashion?
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