From: "Alex Bennée" <alex.bennee@linaro.org>
To: Chunyan Liu <cyliu@suse.com>
Cc: kwolf@redhat.com, qemu-devel@nongnu.org, stefanha@redhat.com
Subject: Re: [Qemu-devel] [PATCH] qemu-img: set nocow flag to new file
Date: Thu, 14 Nov 2013 09:44:42 +0000 [thread overview]
Message-ID: <p1iovvxqph.fsf@linaro.org> (raw)
In-Reply-To: <1384416928-3441-1-git-send-email-cyliu@suse.com>
cyliu@suse.com writes:
> Set NOCOW flag to newly created images to solve performance issues on btrfs.
>
> Btrfs has terrible performance when hosting VM images, even more when the guest
> in those VM are also using btrfs as file system. One way to mitigate this bad
> performance is to turn off COW attributes on VM files (since having copy on
> write for this kind of data is not useful).
<snip>
It's been a while since I had to mess with this performance mystery but
I recall you also need to ensure the partition needs to be mounted with
the nodatacow mount option. Unless this has changed we should probably
warn the user about that.
--
Alex Bennée
next prev parent reply other threads:[~2013-11-14 9:44 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-11-14 8:15 [Qemu-devel] [PATCH] qemu-img: set nocow flag to new file Chunyan Liu
2013-11-14 9:17 ` Kevin Wolf
2013-11-14 14:23 ` Alex Bligh
2013-11-14 14:28 ` Alex Bligh
2013-11-15 4:05 ` Chunyan Liu
2013-11-15 12:26 ` Kevin Wolf
2013-11-14 9:44 ` Alex Bennée [this message]
2013-11-14 10:14 ` Kevin Wolf
2013-11-15 9:38 ` Stefan Hajnoczi
2013-11-18 4:54 ` Chunyan Liu
2013-11-18 9:57 ` Stefan Hajnoczi
2013-12-10 22:23 ` Alex Bennée
2013-12-11 8:29 ` Stefan Hajnoczi
2013-12-18 14:24 ` Daniel P. Berrange
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