[Beowulf] Re: how large of an installation have people used NFS
with? would 300 mounts kill performance?
rpnabar at gmail.com
Thu Sep 10 08:44:41 PDT 2009
On Wed, Sep 9, 2009 at 3:38 PM, Greg Keller <Greg at keller.net> wrote:
> "It all depends" -- Anonymous Cluster expert
Thanks Greg. And I hate that anonymous expert. He's the bane of my
current existence. I even get nightmares with his ghastly face in
> I routinely run NFS with 300+ nodes, but "it all depends" on the
> applications' IO profiles.
50% projected runtime is with an application with negligible reads
and writes (VASP). The other 50% goes to an app. (DACAPO) which strace
shows to be using 10% of its runtime devoted to I/O. Mostly seeks.
More reads than writes. Multiple small reads and writes. All cores
doing I/O not a central master core.
>For example, Lot's of nodes reading and writing
> different files in a generically staggered fashion,
How do you enforce the staggering? Do people write staggered I/O codes
themselves? Or can on alliviate this problem by scheduler settings?
> Luster or eventually pNFS if things get ugly. But not all NFS servers are
> created equal, and a solid purpose built appliance may handle loads a
> general purpose linux NFS server won't.
Disk array connected to generic Linux server? Or standalone
What exactly does a "solid purpose built appliance" offer that a
Generic Linux server (well configured) connected to an array of disks
does not offer?
> The bottleneck is more likely the File-server's Nic and/or it's Back-end
> storage performance. If the file-server is 1GbE attached then having a
> strong network won't help NFS all that much. 10GbE attached will keep up
> with a fair number of raided disks on the back-end. Load the NFS server up
> with a lot of RAM and you could keep a lot of nodes happy if they are
> reading a common set of files in parallel.
Yup; I'm going for at least 24 GB RAM and twin 10 GigE cards
connecting the file server to the switch.
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