| From: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> |
|---|---|
| To: | "Jim C(dot) Nasby" <jnasby(at)pervasive(dot)com> |
| Cc: | Tino Wildenhain <tino(at)wildenhain(dot)de>, Javier Somoza <jsomoza(at)pandasoftware(dot)es>, pgsql-performance(at)postgresql(dot)org |
| Subject: | Re: fsync and battery-backed caches |
| Date: | 2006-02-28 01:06:13 |
| Message-ID: | 200602280106.k1S16DK16068@candle.pha.pa.us |
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| Lists: | pgsql-performance |
Jim C. Nasby wrote:
> On Mon, Feb 27, 2006 at 11:12:57AM +0100, Tino Wildenhain wrote:
> > Javier Somoza schrieb:
> > >
> > > Hi all
> > >
> > > Is it secure to disable fsync havin battery-backed disk cache?
> > >
> > > Thx
> > >
> > No. fsync moves the data from OS memory cache to disk-adaptor
> > cache which is required to benefit from battery backup.
>
> More importantly, in guarantees that data is committed to non-volatile
> storage in such a way that PostgreSQL can recover from a crash without
> corruption.
>
> If you have a battery-backed controller and turn on write caching you
> shouldn't see much effect from fsync anyway.
We do mention battery-backed cache in our docs:
http://www.postgresql.org/docs/8.1/static/wal.html
If it is unclear, please let us know.
--
Bruce Momjian http://candle.pha.pa.us
SRA OSS, Inc. http://www.sraoss.com
+ If your life is a hard drive, Christ can be your backup. +
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