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From: Craig Ringer <craig@postnewspapers.com.au>
To: Ben Chobot <bench@silentmedia.com>
Cc: Ryan Wexler <ryan@iridiumsuite.com>
Cc: PostgreSQL - Performance <pgsql-performance@postgresql.org>
Subject: Re: performance on new linux box
Date: Fri, 16 Jul 2010 19:17:53 +0800
Message-ID: <4C403FE1.8080209@postnewspapers.com.au> (raw)
In-Reply-To: <A6461AB5-0812-4C86-9BF4-3C0EA36148A7@silentmedia.com>
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	<A6461AB5-0812-4C86-9BF4-3C0EA36148A7@silentmedia.com>

On 16/07/10 06:18, Ben Chobot wrote:

> There are also caches on all your disk drives. Write caching there is always dangerous, which is why almost all raid cards always disable the hard drive write caching, with or without a BBU. I'm not even sure how many raid cards let you enable the write cache on a drive... hopefully, not many.

AFAIK Disk drive caches can be safe to leave in write-back mode (ie
write cache enabled) *IF* the OS uses write barriers (properly) and the
drive understands them.

Big if.

--
Craig Ringer



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