| From: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> |
|---|---|
| To: | Richard Huxton <dev(at)archonet(dot)com> |
| Cc: | Mattias Kregert <mattias(at)kregert(dot)se>, Karsten Hilbert <Karsten(dot)Hilbert(at)gmx(dot)net>, PostgreSQL List <pgsql-general(at)postgresql(dot)org> |
| Subject: | Re: Datatypes and performance |
| Date: | 2003-07-21 02:10:20 |
| Message-ID: | 200307210210.h6L2AKQ12895@candle.pha.pa.us |
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| Lists: | pgsql-general |
Richard Huxton wrote:
> > If the answer is "yes", then I understand the use of FSYNC.
> >
> > If the answer is "no", then i don't see the point in using FSYNC at all.
>
> The answer is "yes" providing:
> 1. Your hardware didn't suffer a failure during the outage.
> 2. Your disks don't like to the operating-system.
>
> The second point is important - some disks have write-cache enabled and report
> "done" when data is written to the cache not the platter. Google for
> discussion.
The problem here is whether write-cache is enabled _and_ the disk drive
doesn't use some trick of using the disk drive rotational energy to
ensure that the write cache gets flushed to disk on a power failure, or
perhaps uses some short-term battery to make sure the data gets flushed.
--
Bruce Momjian | http://candle.pha.pa.us
pgman(at)candle(dot)pha(dot)pa(dot)us | (610) 359-1001
+ If your life is a hard drive, | 13 Roberts Road
+ Christ can be your backup. | Newtown Square, Pennsylvania 19073
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