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Re: [Qemu-devel] [RFC] qed: Add QEMU Enhanced Disk format
From: |
Stefan Hajnoczi |
Subject: |
Re: [Qemu-devel] [RFC] qed: Add QEMU Enhanced Disk format |
Date: |
Fri, 10 Sep 2010 12:33:09 +0100 |
On Fri, Sep 10, 2010 at 12:25 PM, Avi Kivity <address@hidden> wrote:
> On 09/10/2010 02:14 PM, Avi Kivity wrote:
>>
>>>
>>> qcow2 is not a properly designed image format. It was a weekend hacking
>>> session from Fabrice that he dropped in the code base and never really
>>> finished doing what he originally intended. The improvements that have been
>>> made to it are almost at the heroic level but we're only hurting our users
>>> by not moving on to something better.
>>>
>>
>> I don't like qcow2 either. But from a performance perspective, it can be
>> made equivalent to qed with some effort. It is worthwhile to expend that
>> effort rather than push the burden to users.
>
> btw, despite being not properly designed, qcow2 is able to support TRIM.
> qed isn't able to, except by leaking clusters on shutdown. TRIM support is
> required unless you're okay with the image growing until it is no longer
> sparse (the lack of TRIM support in guests make sparse image formats
> somewhat of a joke, but nobody seems to notice).
Anthony has started writing up notes on trim for qed:
http://wiki.qemu.org/Features/QED/Trim
I need to look at the actual ATA and SCSI specs for how this will
work. The issue I am concerned with is sub-cluster trim operations.
If the trim region is less than a cluster, then both qed and qcow2
don't really have a way to handle it. Perhaps we could punch a hole
in the file, given a userspace interface to do this, but that isn't
ideal because we're losing sparseness again.
Stefan
- Re: [Qemu-devel] [RFC] qed: Add QEMU Enhanced Disk format, (continued)
- Re: [Qemu-devel] [RFC] qed: Add QEMU Enhanced Disk format, Kevin Wolf, 2010/09/08
- Re: [Qemu-devel] [RFC] qed: Add QEMU Enhanced Disk format, Avi Kivity, 2010/09/09
- Re: [Qemu-devel] [RFC] qed: Add QEMU Enhanced Disk format, Avi Kivity, 2010/09/09
- Re: [Qemu-devel] [RFC] qed: Add QEMU Enhanced Disk format, Anthony Liguori, 2010/09/09
- [Qemu-devel] Re: [RFC] qed: Add QEMU Enhanced Disk format, Paolo Bonzini, 2010/09/09
- [Qemu-devel] Re: [RFC] qed: Add QEMU Enhanced Disk format, Anthony Liguori, 2010/09/09
- Re: [Qemu-devel] Re: [RFC] qed: Add QEMU Enhanced Disk format, Christoph Hellwig, 2010/09/09
- [Qemu-devel] Re: [RFC] qed: Add QEMU Enhanced Disk format, Avi Kivity, 2010/09/10
- Re: [Qemu-devel] [RFC] qed: Add QEMU Enhanced Disk format, Avi Kivity, 2010/09/10
- Re: [Qemu-devel] [RFC] qed: Add QEMU Enhanced Disk format, Avi Kivity, 2010/09/10
- Re: [Qemu-devel] [RFC] qed: Add QEMU Enhanced Disk format,
Stefan Hajnoczi <=
- Re: [Qemu-devel] [RFC] qed: Add QEMU Enhanced Disk format, Avi Kivity, 2010/09/10
- Re: [Qemu-devel] [RFC] qed: Add QEMU Enhanced Disk format, Anthony Liguori, 2010/09/10
- Re: [Qemu-devel] [RFC] qed: Add QEMU Enhanced Disk format, Christoph Hellwig, 2010/09/10
- Re: [Qemu-devel] [RFC] qed: Add QEMU Enhanced Disk format, Anthony Liguori, 2010/09/10
- Re: [Qemu-devel] [RFC] qed: Add QEMU Enhanced Disk format, Kevin Wolf, 2010/09/10
- Re: [Qemu-devel] [RFC] qed: Add QEMU Enhanced Disk format, Anthony Liguori, 2010/09/10
- Re: [Qemu-devel] [RFC] qed: Add QEMU Enhanced Disk format, Kevin Wolf, 2010/09/10
- Re: [Qemu-devel] [RFC] qed: Add QEMU Enhanced Disk format, Anthony Liguori, 2010/09/10
- Re: [Qemu-devel] [RFC] qed: Add QEMU Enhanced Disk format, Kevin Wolf, 2010/09/10
- Re: [Qemu-devel] [RFC] qed: Add QEMU Enhanced Disk format, Miguel Di Ciurcio Filho, 2010/09/10