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Re: Investigating IO Saturation

From: Brad Nicholson <bnichols(at)ca(dot)afilias(dot)info>
To: "Joshua D(dot) Drake" <jd(at)commandprompt(dot)com>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: Investigating IO Saturation
Date: 2006-01-24 17:03:56
Message-ID: 43D65DFC.2040107@ca.afilias.info (view raw or flat)
Thread:
Lists: pgsql-performance
Joshua D. Drake wrote:

> Brad Nicholson wrote:
>
>> I'm investigating a potential IO issue.  We're running 7.4 on AIX 
>> 5.1.  During periods of high activity (reads, writes, and vacuums), 
>> we are seeing iostat reporting 100% disk usage.  I have a feeling 
>> that the iostat numbers are misleading.  I can make iostat usage jump 
>> from less than 10% to greater than 95% by running a single vacuum 
>> against a moderate sized table (no noticeable change in the other 
>> activity).
>>
> Well that isn't surprising. Vacuum is brutal especially on 7.4 as that 
> is pre background writer. What type of IO do you have available (RAID, 
> SCSI?)
>
Data LUN is RAID 10, wal LUN is RAID 1.


-- 
Brad Nicholson  416-673-4106    bnichols(at)ca(dot)afilias(dot)info
Database Administrator, Afilias Canada Corp.



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