From: Peter Kovacs <maxottovonstirlitz@gmail.com>
To: Jeff Davis <pgsql@j-davis.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Carlos Moreno <moreno_pg@mochima.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: Two hard drives --- what to do with them?
Date: Tue, 27 Feb 2007 01:11:24 +0100
Message-ID: <b6e8f2e80702261611j598b1771g3dbcfc9bb1f9cdf2@mail.gmail.com> (raw)
In-Reply-To: <1172526666.10824.315.camel@dogma.v10.wvs>
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<45DF6154.5090205@3times25.net>
<1d4e0c10702231425ke37a732y36e241902fe0aa55@mail.gmail.com>
<45DF94BF.6050904@3times25.net>
<45E0A500.1010707@commandprompt.com>
<45E104DD.3080600@mochima.com>
<2055.1172375931@sss.pgh.pa.us>
<b6e8f2e80702251411q5a27eb53re9c2a299b8e3880a@mail.gmail.com>
<1172526666.10824.315.camel@dogma.v10.wvs>
On 2/26/07, Jeff Davis <pgsql@j-davis.com> wrote:
> On Sun, 2007-02-25 at 23:11 +0100, Peter Kovacs wrote:
> > A related question:
> > Is it sufficient to disable write cache only on the disk where pg_xlog
> > is located? Or should write cache be disabled on both disks?
> >
>
> When PostgreSQL does a checkpoint, it thinks the data pages before the
> checkpoint have successfully made it to disk.
>
> If the write cache holds those data pages, and then loses them, there's
> no way for PostgreSQL to recover. So use a battery backed cache or turn
> off the write cache.
Sorry for for not being familar with storage techonologies... Does
"battery" here mean battery in the common sense of the word - some
kind of independent power supply? Shouldn't the disk itself be backed
by a battery? As should the entire storage subsystem?
Thanks
Peter
>
> Regards,
> Jeff Davis
>
>
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Subject: Re: Two hard drives --- what to do with them?
In-Reply-To: <b6e8f2e80702261611j598b1771g3dbcfc9bb1f9cdf2@mail.gmail.com>
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