From: Avi Kivity <avi@qumranet.com>
To: qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] qcow2 - safe on kill? safe on power fail?
Date: Tue, 22 Jul 2008 22:13:50 +0300 [thread overview]
Message-ID: <4886316E.4080601@qumranet.com> (raw)
In-Reply-To: <20080722161607.GA22535@shareable.org>
Jamie Lokier wrote:
>> It's a simple matter of allocating, making sure the allocation is on
>> disk, and recording that allocation in the tables.
>>
>
> The simple implementations are only safe if sector writes are atomic.
>
> Opinions from Google seem divided about when you can assume that,
> especially when the underlying file or device is not directly mapped
> to disk sectors.
>
That's worrying. I guess always-allocate-on-write solves that (with
versioned roots in well-known places), but that's not qcow2 any more --
it's btrfs. And given that btrfs ought to allow file-level snapshots,
perhaps the direction should be raw files on top of btrfs (which could
be extended to do block sharing, yay!)
--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.
next prev parent reply other threads:[~2008-07-22 19:13 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-03-05 21:18 [Qemu-devel] Signal handling and qcow2 image corruption David Barrett
2008-03-05 21:55 ` Anthony Liguori
2008-03-05 23:48 ` David Barrett
2008-03-06 6:57 ` Avi Kivity
2008-07-21 18:10 ` [Qemu-devel] qcow2 - safe on kill? safe on power fail? Jamie Lokier
2008-07-21 19:43 ` Anthony Liguori
2008-07-21 21:26 ` Jamie Lokier
2008-07-21 22:14 ` Anthony Liguori
2008-07-21 23:47 ` Jamie Lokier
2008-07-22 6:06 ` Avi Kivity
2008-07-22 14:08 ` Anthony Liguori
2008-07-22 14:46 ` Jamie Lokier
2008-07-22 19:11 ` Avi Kivity
2008-07-22 14:32 ` Jamie Lokier
2008-07-21 22:00 ` Andreas Schwab
2008-07-21 22:15 ` Anthony Liguori
2008-07-21 22:22 ` David Barrett
2008-07-21 22:50 ` Anthony Liguori
2008-07-22 6:07 ` Avi Kivity
2008-07-22 14:11 ` Anthony Liguori
2008-07-22 14:36 ` Avi Kivity
2008-07-22 16:16 ` Jamie Lokier
2008-07-22 19:13 ` Avi Kivity [this message]
2008-07-22 20:04 ` Jamie Lokier
2008-07-22 21:25 ` Avi Kivity
2008-07-22 14:22 ` Jamie Lokier
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