Horrible PostgreSQL performance with NFS

Arne Woerner arne_woerner at yahoo.com
Fri Jan 13 13:10:50 PST 2006


--- Slawek Zak <slawek.zak at gmail.com> wrote:
> A couple of days ago I've moved our
> production database from local disks
> to NetAPP filer serving NFS. Performance
> for this server dropped by factor of 10
> if not more.
I would like to suggest some tests (I do not have a clear idea,
why your system becomes slower; a hypothesis will follow below):

1. benchmark the local disc (watch cpu usage via e. g. vmstat 1)
% dd if=/dev/zero of=/some/local/filesystem/a bs=1m count=1000

2. benchmark the NFS filesystem (watch cpu usage via e. g. vmstat
% dd if=/dev/zero of=/some/NFS/filesystem/a bs=1m count=1000

3. test the NIC performance with (again watching the CPU usage
might help)
% ping -s 50000 <nfs-server>
I get 17Mbit/sec which is the actual rate...
neo# ping -s 50000 vaako
PING vaako.riddick.homeunix.org ( 50000 data bytes
50008 bytes from icmp_seq=0 ttl=64 time=46.584 ms

My theory would be, that your NICs need a lot of CPU time, while
your local discs dont need so much CPU time. :-)


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