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Re: [Qemu-devel] live block copy/stream/snapshot discussion

From: Kevin Wolf
Subject: Re: [Qemu-devel] live block copy/stream/snapshot discussion
Date: Thu, 14 Jul 2011 12:07:40 +0200
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv: Gecko/20110428 Fedora/3.1.10-1.fc15 Thunderbird/3.1.10

Am 14.07.2011 12:00, schrieb Stefan Hajnoczi:
> On Thu, Jul 14, 2011 at 10:55 AM, Kevin Wolf <address@hidden> wrote:
>> Am 14.07.2011 11:39, schrieb Stefan Hajnoczi:
>>>  Events:
>>>  On completion the BLOCK_STREAM_COMPLETED event is raised with the following
>>>  fields:
>>>  - device: device name (json-string)
>>>  - len:    size of the device, in bytes (json-int)
>>>  - offset: last offset of completed I/O, in bytes (json-int)
>>>  - error:  error message (json-string, only on error)
>>>  The completion event is raised both on success and on failure.
>> Why do len/offset matter in a completion event?
> For completeness.  You could see it as telling you how much progress
> was made before an error occurred.  In the success case offset will
> always be equal to len.  But in the error case you get the last
> completed progress before error, which could be useful (for example if
> you weren't polling but want to display "Streaming virtio-blk0 failed
> at 33%").

Makes sense.

We also need to define the possible error messages, and probably use an
enum instead of a string.


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