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Re: [Qemu-devel] Re: [RFC] qed: Add QEMU Enhanced Disk format
From: |
H. Peter Anvin |
Subject: |
Re: [Qemu-devel] Re: [RFC] qed: Add QEMU Enhanced Disk format |
Date: |
Fri, 10 Sep 2010 16:49:02 -0700 |
User-agent: |
Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.8) Gecko/20100806 Fedora/3.1.2-1.fc13 Thunderbird/3.1.2 |
On 09/06/2010 05:45 AM, Anthony Liguori wrote:
>>
>> Before inventing yet another image format, you certainly have checked
>> the existing ones.
>
> Obviously, yes.
>
> Here are the issues:
>
> cow.c: it's cow of an otherwise sparse file. An important reason for
> implementing a format is the ability to copy (or scp) an image without
> special tools.
>
> qcow2.c: the refcount, cow cluster, and compression make an
> implementation seeking integrity and performance challenging.
>
> vmdk.c: we feel it's important for qemu to have a block format with a
> gpl friendly specification that we have a say in
>
> vhd/vpc.c: same as vmdk with the addition that the OSP is known to not
> be gpl friendly
>
> vdi.c: uses a bitmap instead of a two level table. An advantage of a
> two level table is that it allows image resize without much fuss.
>
> qcow.c: it lacks extensibility and compression means that there's no
> guarantee that blocks are a fixed size. This makes it very difficult to
> implement a high performance block format without having two separate
> code paths.
>
Okay... how about, say, Linux LVM2 format?
-hpa
- Re: [Qemu-devel] [RFC] qed: Add QEMU Enhanced Disk format, (continued)
[Qemu-devel] Re: [RFC] qed: Add QEMU Enhanced Disk format, Kevin Wolf, 2010/09/06
Re: [Qemu-devel] Re: [RFC] qed: Add QEMU Enhanced Disk format, Anthony Liguori, 2010/09/06
- Re: [Qemu-devel] Re: [RFC] qed: Add QEMU Enhanced Disk format,
H. Peter Anvin <=
Re: [Qemu-devel] [RFC] qed: Add QEMU Enhanced Disk format, Daniel P. Berrange, 2010/09/06
Re: [Qemu-devel] [RFC] qed: Add QEMU Enhanced Disk format, Anthony Liguori, 2010/09/06