From: | Brad Nicholson <bnichols(at)ca(dot)afilias(dot)info> |
---|---|
To: | pgsql-performance(at)postgresql(dot)org |
Subject: | 7.4 Checkpoint Question |
Date: | 2007-11-29 15:10:54 |
Message-ID: | 1196349054.5651.19.camel@bnicholson-desktop |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-performance |
I have a legacy system still on 7.4 (I know, I know...the upgrade is
coming soon).
I have a fairly big spike happening once a day, every day, at the same
time. It happens during a checkpoint, no surprise there. I know the
solution to the problem (upgrade to a modern version), but what I'm
looking for as an explanation as to why one particular checkpoint would
be so bad on a low volume system, so I can appease certain management
concerns.
This is a _really _low volume system, less than 500 writes/hour. Normal
operation sees checkpoint related spikes of around 200-300 milliseconds.
We always checkpoint at the checkpoint timeout (every 5 minutes).
During this one checkpoint, I'm seeing transactions running 2-3 seconds.
During this time, writes are < 5/minute.
Relevant settings:
shared_buffers = 10000
checkpoint_segments = 30
checkpoint_timeout = 300
What gives?
--
Brad Nicholson 416-673-4106
Database Administrator, Afilias Canada Corp.
From | Date | Subject | |
---|---|---|---|
Next Message | Tom Lane | 2007-11-29 15:32:23 | Re: Query only slow on first run |
Previous Message | Gregory Stark | 2007-11-29 11:59:51 | Re: TB-sized databases |