Don't ever have WAL and data on the same OS volume as ext3.
If data=writeback, performance will be fine, data integrity will be ok for WAL, but data integrity will not be
sufficientfor the data partition.
If data=ordered, performance will be very bad, but data integrity will be OK.
This is because an fsync on ext3 flushes _all dirty pages in the file system_ to disk, not just those for the file
beingfsync'd.
One partition for WAL, one for data. If using ext3 this is essentially a performance requirement no matter how your
arrayis set up underneath.
On Aug 13, 2010, at 11:41 AM, Greg Smith wrote:
> Bruce Momjian wrote:
>> We recomment 'data=writeback' for ext3 in our docs
>>
>
> Only for the WAL though, which is fine, and I think spelled out clearly
> enough in the doc section you quoted. Ken's system has one big RAID
> volume, which means he'd be mounting the data files with 'writeback'
> too; that's the thing to avoid.
>
> --
> Greg Smith 2ndQuadrant US Baltimore, MD
> PostgreSQL Training, Services and Support
> greg@2ndQuadrant.com www.2ndQuadrant.us
>
>
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