Message-ID: <50B65185.6010005@optionshouse.com>
Date: Wed, 28 Nov 2012 12:01:41 -0600
From: Shaun Thomas <sthomas@optionshouse.com>
Reply-To: <sthomas@optionshouse.com>
Organization: Peak6
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To: =?ISO-8859-1?Q?Niels_Kristian_Schj=F8dt?= <nielskristian@autouncle.com>,
	"pgsql-performance@postgresql.org" <pgsql-performance@postgresql.org>
Subject: Re: Optimize update query
References: <1C199C0D-13DF-47B3-944A-B0560C6D2E5A@autouncle.com>
	<50B61ABF.4070000@optionshouse.com>, <50B6223B.6000100@mejor.pl>
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	<CAC9DA03-64C2-45E2-9B88-703F9768F574@autouncle.com>
	<50B641AD.3020204@optionshouse.com>
	<1E87B44E-A22E-4790-A737-C8EAF504C58E@autouncle.com>
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On 11/28/2012 11:44 AM, Niels Kristian Schj=F8dt wrote:

> Thanks a lot - on the server I already have one additional SSD 250gb
> disk, that I don't use for anything at the moment.

Goooood. An SSD would actually be better for your data, as it follows
more random access patterns, and xlogs are more sequential. But it's
better than nothing.

And yes, you'd be better off with a RAID-1 of two of these SSDs, because
the xlogs are critical to database health. You have your archived copy
due to the rsync, which helps. But if you had a crash, there could
potentially be a need to replay unarchived transaction logs, and you'd
end up with some data loss.

> BTW. as you might have seen from the .conf I have a second slave
> server with the exact same setup, which currently runs as a hot
> streaming replication slave. I might ask a stupid question here, but
> this does not affect the performance of the master does it?

Only if you're using synchronous replication. From what I saw in the
config, that isn't the case.


--
Shaun Thomas
OptionsHouse | 141 W. Jackson Blvd. | Suite 500 | Chicago IL, 60604
312-444-8534
sthomas@optionshouse.com

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