From: Jamie Lokier <jamie@shareable.org>
To: qemu-devel@nongnu.org
Cc: Laurent Vivier <Laurent.Vivier@bull.net>
Subject: Re: [Qemu-devel] [PATCH] Align file accesses with cache=off (O_DIRECT)
Date: Wed, 30 Apr 2008 01:05:13 +0100 [thread overview]
Message-ID: <20080430000513.GC25408@shareable.org> (raw)
In-Reply-To: <48174B0B.5070904@suse.de>
Kevin Wolf wrote:
> I think we agree that it's mostly item 3 why one would use O_DIRECT with
> qemu. In terms of reliability, it is important that the data really is
> written to the disk when the guest OS thinks so. But when for example
> qemu crashes, I don't think it's too important if 40% or 50% of a
> snapshot have already been written - it's unusable anyway. A sync
> afterwards could be enough there.
A call to fsync() after writing provides the same guarantee as
O_DIRECT, or stronger if fsync() does a hard disk cache flush, which
O_DIRECT does not.
-- Jamie
next prev parent reply other threads:[~2008-04-30 0:05 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-04-17 13:31 [Qemu-devel] [PATCH] Align file accesses with cache=off (O_DIRECT) Kevin Wolf
2008-04-28 15:34 ` Kevin Wolf
2008-04-29 9:01 ` Laurent Vivier
2008-04-29 14:49 ` Kevin Wolf
2008-04-29 15:48 ` Laurent Vivier
2008-04-29 16:21 ` Kevin Wolf
2008-04-29 16:48 ` Laurent Vivier
2008-04-30 9:21 ` Kevin Wolf
2008-04-30 9:59 ` Laurent Vivier
2008-04-30 12:08 ` Kevin Wolf
2008-04-30 14:30 ` Blue Swirl
2008-04-30 21:05 ` Kevin Wolf
2008-05-01 14:35 ` Blue Swirl
2008-05-01 17:55 ` Kevin Wolf
2008-05-06 8:44 ` Kevin Wolf
2008-05-06 9:02 ` Laurent Vivier
2008-05-06 16:42 ` Blue Swirl
2008-05-06 16:56 ` Kevin Wolf
2008-05-06 17:23 ` Blue Swirl
2008-04-30 0:05 ` Jamie Lokier [this message]
2008-04-30 0:02 ` Jamie Lokier
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