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Date: Wed, 25 Aug 2010 08:46:15 -0500
From: Anthony Liguori <anthony@codemonkey.ws>
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Subject: [Qemu-devel] Re: [RFC][STABLE 0.13] Revert "qcow2: Use
 bdrv_(p)write_sync for metadata writes"
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To: Avi Kivity <avi@redhat.com>
Cc: Kevin Wolf <kwolf@redhat.com>, stefanha@gmail.com, mjt@tls.msk.ru, qemu-devel@nongnu.org, hch@lst.de

On 08/25/2010 08:23 AM, Avi Kivity wrote:
>  On 08/25/2010 03:46 PM, Anthony Liguori wrote:
>>
>> If we had another disk format that only supported growth and metadata 
>> for a backing file, can you think of another failure scenario?
>
> btw, only supporting growth is a step backwards.  Currently 
> file-backed disks keep growing even the guest-used storage doesn't 
> grow, since once we allocate something we never release it.  But 
> eventually guests will start using TRIM or DISCARD or however it's 
> called, and then we can expose it and reclaim unused blocks.

BTW, something that had the features of qcow2 that people actually used 
andwas fully asynchronous, performed well, and had a high degree of 
confidence in data integrity would be a major step forward, not backwards.

Regards,

Anthony Liguori