Hi Dave,
We have LAM setup over NFS here on a single gigabit ethernet switch.
I have noticed performance affects with large numbers of files.
We have an 8 node cluster with one machine serving the others with an 80
Gig ide disk for nfs mount.
At one point I was running 5 copies of lam on 5 of the machines (I think
there were 8 processes in each execution - ie., 8 ranks per node), all
of which were writing to file ( on the same disk ). I was collecting
real time data and this was way off on all the machines except the one
which had the 80 gig disk local.
I didn't actually setup the nfs myself and as yet haven't been able to
get anyone to look at it, I have feeling there may be some config
problems. Anyway it's probably something you should be aware of
especially if you're collecting real time data. I solved the problem by
writing a script so that the data is output to the local disk (/tmp/)
during the run and then copied across when finished.
Cheers
Mike
Dave Hagedorn wrote:
> Hi everyone,
>
> Just wondering if anyone has noticed any performance differences in
> runnnig lam off of an NFS mount as opposed to running locally.
>
> We've got a 14-node cluster set up where I work. There is also a
> storage server with a RAID array. All of the nodes and storage server
> are connected with gigabit ethernet through a single switch. We've
> stored lam + our program (LS-DYNA) on an NFS mount which all of the
> nodes access. In addition, our home directories are mounted via NFS,
> so all output fies from LS-DYNA gets sent across the netowrk. These
> files typically amount to 2 GB or so, usually written over the course
> of a days or more.
>
> Does anyone think this setup could cmpromise overall performance? We
> haven't tried intstalling anything locally - the NFS setup is really
> convenient.
>
> Thanks in advance,
>
> Dave Hagedorn
>
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