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Date: Mon, 20 Sep 2010 10:51:47 -0500
From: Anthony Liguori <anthony@codemonkey.ws>
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Subject: Re: [Qemu-devel] [RFC] block-queue: Delay and batch metadata writes
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To: Kevin Wolf <kwolf@redhat.com>
Cc: qemu-devel@nongnu.org

On 09/20/2010 10:08 AM, Kevin Wolf wrote:
>
>> If you're comfortable with a writeback cache for metadata, then you
>> should also be comfortable with a writeback cache for data in which
>> case, cache=writeback is the answer.
>>      
> Well, there is a difference: We don't pollute the host page cache with
> guest data and we don't get a virtual "disk cache" as big as the host
> RAM, but only a very limited queue of metadata.
>    

Would it be a mortal sin to open the file twice and have a cache=none 
version for data and cache=writeback for metadata?

The two definitely aren't consistent with each other but I think the 
whole point here is that we don't care.

It opens up some other possibilities too like cache=none for data and 
cache=writethrough for metadata which may be a useful combination.

Regards,

Anthony Liguori