From: Chris Mason <mason@suse.com>
To: Hans Reiser <reiser@namesys.com>
Cc: linux-fsdevel@vger.kernel.org, akpm@osdl.org,
reiserfs-dev@namesys.com,
Martin Steigerwald <Martin@lichtvoll.de>
Subject: Re: [PATCH 0/2] enable write barriers by default
Date: Sat, 5 Aug 2006 08:45:19 -0400 [thread overview]
Message-ID: <20060805124519.GH1048@watt.suse.com> (raw)
In-Reply-To: <44D412FB.8080902@namesys.com>
On Fri, Aug 04, 2006 at 09:39:39PM -0600, Hans Reiser wrote:
>
> Please explain when cache flushes occur now.
Without them enabled? Never. With them enabled on every commit and/or
fsync.
> For every fsync on a drive
> that does not support write barriers? Which drives support it?
Most IDE and SATA drives.
>
> Did this only get enabled now because it is only now that someone from
> the press is paying attention to it?
No, it has been enabled by default in the SUSE kernels for a long time
(two enterprise releases now sles9 and sles10). I wanted to bring the
discussion about it into mainline.
>
> This is the price we paid for losing Andre, yes?
This is the price we pay for drives turning writeback cache on by
default. It happens for performance, because without tagging write
though caches give horrible write speeds. It is slower than not doing
IO (writeback cache) but faster than turning writeback caches off.
Exact benchmarks vary by drive, but it is never slower than
write-through caching, and almost always faster.
-chris
prev parent reply other threads:[~2006-08-05 12:45 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-08-04 13:51 [PATCH 0/2] enable write barriers by default Chris Mason
2006-08-04 13:53 ` [PATCH 1/2] Make reiserfs default to barrier=flush Chris Mason
2006-08-04 13:55 ` [PATCH 2/2] make ext3 mount default to barrier=1 Chris Mason
2006-08-05 3:39 ` [PATCH 0/2] enable write barriers by default Hans Reiser
2006-08-05 12:45 ` Chris Mason [this message]
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