Re: wal_sync_methods for AIX

[Erik Jones <erik(at)myemma(dot)com>]

On Feb 15, 2008, at 3:55 PM, Dan Langille wrote:

> We're using PostgreSQL 8.1.11 on AIX 5.3 and we've been doing some  
> playing around
> with various settings.  So far, we've (I say we, but it's another  
> guy doing the work) found
> that open_datasync seems better than fsync.  By how much, we have  
> not yet determined,
> but initial observations are promising.

Here's a good explanation (by the Greg Smith) on the different sync  
methods.  It basically says that if you have open_datasync available,  
it'll probably beat everything else.

> Our tests have been on a p550 connected to DS6800 array using pgbench.
>
> One nasty behaviour we have seen is long running commits. Initial  
> thoughts connected
> them with checkpoints, but the long running commits do not  
> correlate with checkpoints being
> written.  Have you seen this behaviour?
>
> FYI, 8.3.0 is not an option for us in the short term.
>
> What have you been using on AIX and why?

I really don't know anything about AIX, but are you sure that these  
long running commits are directly correlated with using open_datasync?

Erik Jones

DBA | Emma®
erik(at)myemma(dot)com
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