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Date: Mon, 11 Jun 2012 09:59:42 +0200
From: Kevin Wolf <kwolf@redhat.com>
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Subject: Re: [Qemu-devel] CoW image commit+shrink(= make_empty) support
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To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Stefan Hajnoczi <stefanha@gmail.com>, jcody@redhat.com, Zhi Hui Li <zhihuili@linux.vnet.ibm.com>, Taisuke Yamada <tai@rakugaki.org>, qemu-devel@nongnu.org

Am 10.06.2012 18:10, schrieb Paolo Bonzini:
> Il 08/06/2012 19:57, Kevin Wolf ha scritto:
>>>>
>>>> I agree, doing it like mirroring for new writes on the top layer makes
>>>> sense, as long as you are willing to violate the (optional) speed
>>>> parameter.  I wouldn't think violating the speed parameter in that case
>>>> would be an issue, as long as it is a documented affect of performing a
>>>> live commit on the active (top) layer.
>> The question is what the speed parameter really means for a live commit
>> block job (or for an active mirror). I think it would make sense to
>> limit only the speed of I/O that doesn't come from the guest but is from
>> the background copying.
> 
> Not necessarily, you can throttle the copying speed.  If the I/O from
> the guest has bursts, you will pick up the work later when the rate
> calms down.

Then it's not an active mirror any more, but a passive one.

Kevin