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Re: what could cause inserts getting queued up and db locking??

From: "Brian Maguire" <bmaguire(at)vantage(dot)com>
To: "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: <pgsql-general(at)postgresql(dot)org>,"Bruce Momjian" <pgman(at)candle(dot)pha(dot)pa(dot)us>
Subject: Re: what could cause inserts getting queued up and db locking??
Date: 2004-10-28 15:24:53
Message-ID: 4BAFBB6B9CC46F41B2AD7D9F4BBAF78501C9BB51@vt-pe2550-001.vantage.vantage.com (view raw or flat)
Thread:
Lists: pgsql-general
Tom,
You hit the nail on the head with what we did.  We did two things and it
made a world of difference.  

We moved from RAID 5 SCSII drives to our EMC SAN RAID 10 and adjusted
the checkpoint segments from 15 to 30.  

The bottleneck disappeared totally and actually have never seen better
performance.  

Two questions:  

What are the implications to further increasing the checkpoint so say
40?

Also how does 8.0's background-writer feature work and what are going to
benefits?

Brian

-----Original Message-----
From: Tom Lane [mailto:tgl(at)sss(dot)pgh(dot)pa(dot)us] 
Sent: Tuesday, October 26, 2004 5:59 PM
To: Brian Maguire
Cc: pgsql-general(at)postgresql(dot)org
Subject: Re: [GENERAL] what could cause inserts getting queued up and db
locking?? 

Brian Maguire <bmaguire(at)vantage(dot)com> wrote:
>> We though there might be locking, but noticed that there were not any
>> queries in wait mode indicating that no statements were blocked by
>> another statement's lock.

In that case it's not a locking problem, but just a resource-saturation
problem.  I'm wondering if you are maxing out your disk drives'
throughput.

Are the slowdowns correlated with checkpoints?  (Watch to see if there
is a postmaster child process spawned for checkpointing when it
happens.)  Fooling with checkpoint intervals might help some, though
I suspect the only real answer will be 8.0's background-writer feature.

			regards, tom lane

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Subject: Re: what could cause inserts getting queued up and db locking??
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