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Re: [Qemu-devel] Re: Strategic decision: COW format
From: |
Markus Armbruster |
Subject: |
Re: [Qemu-devel] Re: Strategic decision: COW format |
Date: |
Wed, 23 Feb 2011 14:20:25 +0100 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/23.1 (gnu/linux) |
Chunqiang Tang <address@hidden> writes:
[...]
> Now let’s talk about features. It seems that there is great interest in
> QCOW2’ internal snapshot feature. If we really want to do that, the right
Great interest? Its use cases are demo, debugging, testing and such.
Kind of useful for developers, but I wouldn't want to use it in anger.
Nice to have if we can get it cheaply, but I'm not prepared to pay much
for it in performance or complexity, and I doubt I'm the only one.
Users always say "yes" when you ask them whether they need some feature.
Hence, the question is useless. A better question to ask is "how much
are you willing to pay for it?"
> solution is to follow VMDK’s approach of storing each snapshot as a
> separate COW file (see http://www.vmware.com/app/vmdk/?src=vmdk ), rather
> than using the reference count table. VMDK’s approach can be easily
> implemented for any COW format, or even as a function of the generic block
> layer, without complicating any COW format or hurting its performance. I
> know the snapshots are not really “internal” as stored in a single file
> but instead more like external snapshots, but users don’t care about that
> so long as they support the same use cases. Probably many people who use
> VMware don't even know that the snapshots are stored as separate files. Do
> they care?
I certainly wouldn't.
- [Qemu-devel] Bugs in the VDI Block Device Driver, (continued)
- Re: [Qemu-devel] Re: Strategic decision: COW format, Aurelien Jarno, 2011/02/20
- Re: [Qemu-devel] Re: Strategic decision: COW format, Kevin Wolf, 2011/02/21
- Re: [Qemu-devel] Re: Strategic decision: COW format, Stefan Hajnoczi, 2011/02/21
- Re: [Qemu-devel] Re: Strategic decision: COW format, Kevin Wolf, 2011/02/21
- Re: [Qemu-devel] Re: Strategic decision: COW format, Anthony Liguori, 2011/02/21
- Re: [Qemu-devel] Re: Strategic decision: COW format, Kevin Wolf, 2011/02/21
- Re: [Qemu-devel] Re: Strategic decision: COW format, Chunqiang Tang, 2011/02/22
- Re: [Qemu-devel] Re: Strategic decision: COW format,
Markus Armbruster <=
- Re: [Qemu-devel] Re: Strategic decision: COW format, Markus Armbruster, 2011/02/22
Re: [Qemu-devel] Re: Comparing New Image Formats: FVD vs. QED, Stefan Hajnoczi, 2011/02/16