[Qemu-devel] Re: [RFC][STABLE 0.13] Revert "qcow2: Use bdrv_(p)write_sync for metadata writes"

[Avi Kivity <avi@redhat.com>]

  On 08/25/2010 04:46 PM, Anthony Liguori wrote:
> 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.
>

TRIM/DISCARD is not a feature that people use (esp. as it's not 
available) but we do want to support it in our image formats.

-- 
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