Re: Horrible PostgreSQL performance with NFS

David Miller <dmiller@xxxxxxxxxx> · Sat, 14 Jan 2006 13:09:02 -0500

Arne Woerner wrote:
--- Slawek Zak <slawek.zak@xxxxxxxxx> wrote:

On 1/13/06, Arne Woerner <arne_woerner@xxxxxxxxx> wrote:
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%.

Looks good...

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%.

Looks even better... :-)

3. test the NIC performance with

Filer doesn't respond to large icmp packets.

Ok... This isn't so important, since NFS speed is higher than
local disc speed.

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 account 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.

Hmm...
But why does switching from local disc to NFS makes the PostgreSQL

performance so bad?

It certainly sounds like something is no longer caching things - either 
reads or writes or both - when using NFS.
Does FreeBSD 6.x have a version of lockd that works with the netApp?

--- David
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Re: Horrible PostgreSQL performance with NFS

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