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Date: Wed, 23 Feb 2011 08:23:20 -0600
From: Anthony Liguori <anthony@codemonkey.ws>
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Subject: Re: [Qemu-devel] Re: Strategic decision: COW format
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To: Avi Kivity <avi@redhat.com>
Cc: Kevin Wolf <kwolf@redhat.com>, Chunqiang Tang <ctang@us.ibm.com>, qemu-devel@nongnu.org, Markus Armbruster <armbru@redhat.com>, Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>

On 02/23/2011 07:43 AM, Avi Kivity wrote:
> On 02/22/2011 10:56 AM, Kevin Wolf wrote:
>> *sigh*
>>
>> It starts to get annoying, but if you really insist, I can repeat it
>> once more: These features that you don't need (this is the correct
>> description for what you call "misfeatures") _are_ implemented in a way
>> that they don't impact the "normal" case. And they are it today.
>>
>
> Plus, encryption and snapshots can be implemented in a way that 
> doesn't impact performance more than is reasonable.

We're still missing the existence proof of this, but even assuming it 
existed, what about snapshots?  Are we okay having a feature in a 
prominent format that isn't going to meet user's expectations?

Is there any hope that an image with 1000, 1000, or 10000 snapshots is 
going to have even reasonable performance in qcow2?

Regards,

Anthony Liguori

>   Compression perhaps not, but if you choose compression, then 
> performance is not your top consideration.  That's the case with 
> filesystems that support compression as well.
>