On 1/13/06, Arne Woerner <[EMAIL PROTECTED]> wrote: > Hiho! > > --- Slawek Zak <[EMAIL PROTECTED]> 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
40MB/s. CPU load negligible. I don't have an exact number, as this machine has other processes running. But overall, the system load didn't exceed 5%. > 2. benchmark the NFS filesystem (watch cpu usage via e. g. vmstat > 1) > % dd if=/dev/zero of=/some/NFS/filesystem/a bs=1m count=1000 I saturated fast ethernet on the host with this test. Filer is connected with Gb and can spew around 70MB/s easily. CPU load on the host didn't exceed 4%. > 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 (10.1.1.3): 50000 data bytes > 50008 bytes from 10.1.1.3: icmp_seq=0 ttl=64 time=46.584 ms Filer doesn't respond to large icmp packets. 20000 was the biggest that worked. CPU load negligible. > My theory would be, that your NICs need a lot of CPU time, while > your local discs dont need so much CPU time. :-) I don't think so. Drivers accout for system time. It doesn't exceed 20% of overall load. The postgres processes are very busy doing almost nothing. Semops is most of the work they seem to do. Thanks, /S -- Sławek Żak / UNIX Systems Administrator
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