Re: how unsafe (or worst scenarios) when setting fsync

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Simon Riggs <simon(at)2ndquadrant(dot)com>
Cc: guoping(dot)zhang(at)nec(dot)com(dot)au, pgsql-performance(at)postgresql(dot)org, "Guoping Zhang (E-mail)" <guopingz(at)nstc(dot)nec(dot)com(dot)au>
Subject: Re: how unsafe (or worst scenarios) when setting fsync
Date: 2006-04-27 14:57:46
Message-ID: 11142.1146149866@sss.pgh.pa.us
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Simon Riggs <simon(at)2ndquadrant(dot)com> writes:
> On Thu, 2006-04-27 at 16:31 +1000, Guoping Zhang wrote:
>> Can we set fsync OFF for the performance benefit, have the risk of only 5
>> minutes data loss or much worse?

> Thats up to you.

> fsync can be turned on and off, so you can make critical changes with
> fsync on, then continue with fsync off.

I think it would be a mistake to assume that the behavior would be
nice clean "we only lost recent changes". Things could get arbitrarily
badly corrupted if some writes make it to disk and some don't.

regards, tom lane

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