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Date: Wed, 16 Feb 2011 13:34:47 +0100
From: Kevin Wolf <kwolf@redhat.com>
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Subject: Re: [Qemu-devel] Re: Comparing New Image Formats: FVD vs. QED
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To: Chunqiang Tang <ctang@us.ibm.com>
Cc: qemu-devel@nongnu.org

Am 15.02.2011 20:45, schrieb Chunqiang Tang:
>> Chunqiang Tang/Watson/IBM wrote on 01/28/2011 05:13:27 PM:
>> As you requested, I set up a wiki page for FVD at 
> http://wiki.qemu.org/Features/FVD
>> . It includes a summary of FVD, a detailed specification of FVD, and a 
>> comparison of the design and performance of FVD and QED. 
> 
>> See the figure at http://wiki.qemu.org/Features/FVD/Compare . This 
> figure 
>> shows that the file creation throughput of NetApp's PostMark benchmark 
> under 
>> FVD is 74.9% to 215% higher than that under QED.
> 
> Hi Anthony,
> 
> Please let me know if more information is needed. I would appreciate your 
> feedback and advice on the best way to proceed with FVD. 

Yet another file format with yet another implementation is definitely
not what we need. We should probably take some of the ideas in FVD and
consider them for qcow3.

However, I think some of them like the "no-alloc" mode aren't that
useful: If I want the features and the performance of raw, I can just
take raw.

> BTW, I recently added QCOW2 into the performance comparison figure on 
> wiki.

It's obvious why you have only one case for QED (it doesn't support
anything else), but qcow2 works on block devices, too, and you can also
use metadata preallocation. Are you aware of this?

Kevin