From: Joshua Berkus <josh@agliodbs.com>
To: Niels Kristian Schjødt <nielskristian@autouncle.com>
Cc: postgres performance list <pgsql-performance@postgresql.org>
Subject: Re: Risk of data corruption/loss?
Date: Wed, 13 Mar 2013 16:18:38 -0500 (CDT)
Message-ID: <1742777165.26321.1363209518274.JavaMail.root@agliodbs.com> (raw)
In-Reply-To: <90758F5A-C637-4EE8-88B8-EF9AFA5AF576@autouncle.com>
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Neils,
> - Master server with battery back raid controller with 4 SAS disks in
> a RAID 0 - so NO mirroring here, due to max performance
> requirements.
> - Slave server setup with streaming replication on 4 HDD's in RAID
> 10. The setup will be done with synchronous_commit=off and
> synchronous_standby_names = ''
I'd be concerned that, assuming you're making the master high-risk for performance reasons, that the standby would not keep up.
> So as you might have noticed, clearly there is a risk of data loss,
> which is acceptable, since our data is not very crucial. However, I
> have quite a hard time figuring out, if there is a risk of total
> data corruption across both server in this setup? E.g. something
> goes wrong on the master and the wal files gets corrupt. Will the
> slave then apply the wal files INCLUDING the corruption (e.g. an
> unfinished transaction etc.), or will it automatically stop
> restoring at the point just BEFORE the corruption, so my only loss
> is data AFTER the corruption?
Well, in general RAID 1 really just protects you from HDD failure, not more subtle types of corruption which occur onboard an HDD. So from that respect, you haven't increased your chances of data corruption at all; if the master loses a disk, it should just stop operating; a simple check that all WALs are 16MB on the standby would do the rest. I'd be more concerned that you're likely to be yanking and completely rebuilding the master server every 4 or 5 months.
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To: pgsql-performance@postgresql.org
Cc: josh@agliodbs.com, nielskristian@autouncle.com
Subject: Re: Risk of data corruption/loss?
In-Reply-To: <1742777165.26321.1363209518274.JavaMail.root@agliodbs.com>
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