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From: "Denis V. Lunev" <den@virtuozzo.com>
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Date: Mon, 14 Mar 2016 19:27:42 +0300
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Subject: Re: [Qemu-devel] [PATCH v2 0/6] external backup api
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To: Paolo Bonzini <pbonzini@redhat.com>, Stefan Hajnoczi <stefanha@gmail.com>
Cc: Kevin Wolf <kwolf@redhat.com>, Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>, Fam Zheng <famz@redhat.com>, Markus Armbruster <armbru@redhat.com>, qemu-devel <qemu-devel@nongnu.org>, John Snow <jsnow@redhat.com>

On 03/10/2016 08:40 PM, Paolo Bonzini wrote:
>
> On 10/03/2016 18:37, Stefan Hajnoczi wrote:
>> I suggest giving the new NBD command a "type" argument:
>> 0 - SCSI mapped/anchored values according to SCSI Get LBA Status
>> 1 - Dirty/clean, useful for incremental backup and other blocking tracking cases
>>
>> This way we don't impinge on SCSI semantics and the command can be
>> used for both traditional logical block provisioning and dirty bitmap
>> info.
>>
>> When the NBD export is started in QEMU you can optionally associate it
>> with a bitmap.  This bitmap is used to provide type=1 (dirty/clean)
>> status information.
> Good idea.  The precedent in NBD is to use bits 16..31 of the command
> for flags, so it could go there.
>
> Paolo
like this too.

Den