Re: [ccp4bb]: NFS Performance

["David J. Schuller" <djs63@cornell.edu>]

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On Tue, 16 Apr 2002, Martin Singleton wrote:

> We have recently started using Linux (RedHat 7.2) machines in our SGI
> based network.
> All of our user accounts are held on an NFS exported filesystem from an
> SGI server. This filesystem is mounted on the Linux machine as well as the
> other SGIs. Linux sees the filesystem fine, but there appears to be a
> major performance problem when certain CCP4 programs as well as SOLVE on
> the Linux box requires access to this filesystem. The problem seems to
> occur during read/writes of large binary files, which cause programs to
> slow to a crawl, in some cases increasing the run time by two orders of
> magnitude. I have noticed that the programs processor usage often drops to
> < 1% when this occurs and the machine rapidly runs out of memory (1GB
> real!) If the same process is run on the local (ext3) disc only, or on the
> SGI machines, there are no such problems. Obviously the problem lies with
> the Linux-IRIX disc cross-mounting, but so far I have not been able to see
> where, and the documented NFS options do not seem to help. Has anyone else
> noticed this problem, or suggest any solutions ?

NFS v2 vs NFS v3 can be a problem. read the NFS-related 'mount' man page 
for flags to specify one or the other for use in tracking down the 
problem.  Irix supports NFSv3 (except see paragraph below). Linux is also 
supposed to support NFSv3, but i don't know if that support is standard or 
optional in a RedHat install, and i would check for any updates or bug 
fixes related to NFSv3 performance. try "mount" with no options to get a 
list of mount parameters for various disks. on the NFS disks check for 
"v3". check the system log files on both machines for messages about 
trouble with the NFS mounts, these could be indicative of a v2 vs v3 
problem.

are you by chance using automount in conjunction with NFS?  we had similar 
problems sharing disks between Digital Unix Alphas and SGIs. it turned out 
that SGI automount did not support NFS v3.  If you are using automount, 
try switching to autofs, which not only supports NFS v3 (on SGI) but is 
multi-threaded.

the other reply (i forget by whom) was correct that scratch directories 
should be on local disks.

cheers,
=======================================================================
"You can trust me, because I'm in the news media"  -- Dave Barry
=======================================================================
                        David J. Schuller
                        modern man in a post-modern world
                        MacCHESS, Cornell University
                        djs63@cornell.edu