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Re: Tuning Postgres 9.1 on Windows

From: "Walker, James Les" <JAWalker(at)cantor(dot)com>
To: 'Merlin Moncure' <mmoncure(at)gmail(dot)com>
Cc: Thomas Kellerer <spam_eater(at)gmx(dot)net>, "pgsql-performance(at)postgresql(dot)org"<pgsql-performance(at)postgresql(dot)org>
Subject: Re: Tuning Postgres 9.1 on Windows
Date: 2012-05-01 14:44:15
Message-ID: 21BFB59709EBB84DB412ED7F739FFD3B1AC403@TBPINFN0203.cad.local (view raw or flat)
Thread:
Lists: pgsql-performance
I installed the enterprisedb distribution and immediately saw a 400% performance increase. Turning off fsck made it an order of magnitude better. I'm now peaking at over 400 commits per second. Does that sound right?

If I understand what you're saying, then to sustain this high rate I'm going to need a controller that can defer fsync requests from the host because it has some sort of battery backup that guarantees the full write.

-- Les

-----Original Message-----
From: Merlin Moncure [mailto:mmoncure(at)gmail(dot)com] 
Sent: Tuesday, May 01, 2012 9:43 AM
To: Walker, James Les
Cc: Thomas Kellerer; pgsql-performance(at)postgresql(dot)org
Subject: Re: [PERFORM] Tuning Postgres 9.1 on Windows

On Tue, May 1, 2012 at 8:14 AM, Walker, James Les <JAWalker(at)cantor(dot)com> wrote:
> SSD is OCZ-VERTEX3 MI. Controller is LSI SAS2 2008 Falcon. I'm working on installing EDB. Then I can give you some I/O numbers.

It looks like the ssd doesn't have a nv cache and the raid card is a simple sas hba (which likely isn't doing much for the ssd besides masking TRIM).  The OCZ 'pro' versions are the ones with power loss protection (see:
http://hothardware.com/Reviews/OCZ-Vertex-3-Pro-SandForce-SF2000-Based-SSD-Preview/).
 Note the bullet: "Implements SandForce 2582 Controller with power loss data protection".  It doesn't look like the Vertex 3 Pro is out yet.

If my hunch is correct, the issue here is that the drive is being asked to sync data physically and SSD really don't perform well when the controller isn't in control of when and how to sync data.  However full physical sync is the only way to guarantee data is truly safe in the context of a unexpected power loss (an nv cache is basically a compromise on this point).

merlin
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