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Re: Intel SSD

From: Merlin Moncure <mmoncure(at)gmail(dot)com>
To: Sebastian Böhm <seb(at)exse(dot)net>
Cc: pgsql-general(at)postgresql(dot)org
Subject: Re: Intel SSD
Date: 2009-02-11 13:17:20
Message-ID: b42b73150902110517o3f8c45b8l743aac9bb2ede2ae@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-general
On Tue, Feb 10, 2009 at 9:24 PM, Sebastian Böhm <seb(at)exse(dot)net> wrote:
> I consider buying one of these Intel SSDs for my Database (MLC).
>
> I have a few questions regarding this, maybe some of you already have some
> experience with that.
>
> - which files should not be put onto the SSD (pg_clog ? pg_xlog ? ) to
> reduce wear (which may be an issue with the MLC variant)

just shooting from the hip here, but with the MLC drive I'd leave xlog
on the hard drive and put everything else on the SSD.

> - is there really a significant performance gain for random reads on a 30GB
> Database ?

Yes.  read latency is measured in microseconds not milliseconds.

> -are there guides for tuning pg on SSD available ? (I guess some of the
> Planner Cost Constants should be quite differend on an SSD to achive optimal
> performance, as random_page_cost and seq_page_cost may be quite identical )

> currently I have a lot of small random reads/writes causing heavy iowait.

writes could still continue to be a problem.  You are taking a bit of
a gamble going with the MLC drive...lifespan could be an issue and
random writes are not significantly improved vs. traditional hard
drive.

merlin

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