From: Tom Lane <tgl@sss.pgh.pa.us>
To: Simon Riggs <simon@2ndquadrant.com>
Cc: Dan Gorman <dgorman@hi5.com>
Cc: Toru SHIMOGAKI <shimogaki.toru@oss.ntt.co.jp>
Cc: pgsql-performance@postgresql.org
Subject: Re: PITR Backups
Date: Fri, 22 Jun 2007 14:02:44 -0400
Message-ID: <24724.1182535364@sss.pgh.pa.us> (raw)
In-Reply-To: <1182534358.9276.326.camel@silverbirch.site>
References: <7E0807EE-B970-4869-A248-B838E42AD9EE@hi5.com>
<9761.1182472005@sss.pgh.pa.us>
<467B3459.9030808@oss.ntt.co.jp>
<1182509748.9276.178.camel@silverbirch.site>
<31812EEE-22E7-41CD-B70F-CE861681BABC@hi5.com>
<23875.1182532322@sss.pgh.pa.us>
<1182534358.9276.326.camel@silverbirch.site>
"Simon Riggs" <simon@2ndquadrant.com> writes:
> On Fri, 2007-06-22 at 13:12 -0400, Tom Lane wrote:
>> If you saw a problem I'd be inclined to question whether
>> there is some upstream component (OS or disk controller) that's
>> reordering writes.
> Given thats exactly what they do, constantly, I don't think its safe to
> say that it works since we cannot verify whether that has happened or
> not.
If he's trying to snapshot at a level of hardware that's behind a
write-caching disk controller, I agree that that's untrustworthy.
If not, ie if he's snapshotting the actual durable state of the storage
system, then any problems in the snapshot indicate a problem with the
database's ability to recover from a crash. So I don't think you should
tell him to not worry.
regards, tom lane
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, simon@2ndquadrant.com, dgorman@hi5.com, shimogaki.toru@oss.ntt.co.jp
Subject: Re: PITR Backups
In-Reply-To: <24724.1182535364@sss.pgh.pa.us>
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