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 sufficient for 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 being fsync'd.

One partition for WAL, one for data.  If using ext3 this is essentially a 
performance requirement no matter how your array is 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
> g...@2ndquadrant.com   www.2ndQuadrant.us
> 
> 
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