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Re: [Qemu-devel] Re: [PATCH 0/3 v5] Live migration without shared storag

From: Jan Kiszka
Subject: Re: [Qemu-devel] Re: [PATCH 0/3 v5] Live migration without shared storage
Date: Tue, 24 Nov 2009 15:17:54 +0100
User-agent: Mozilla/5.0 (X11; U; Linux i686 (x86_64); de; rv: Gecko/20080226 SUSE/ Thunderbird/ Mnenhy/

Pierre Riteau wrote:
> On 23 nov. 2009, at 19:47, Jan Kiszka wrote:
>> Avi Kivity wrote:
>>> On 11/03/2009 11:40 AM, Liran Schour wrote:
>>>> - Liran
>>>> Avi Kivity<address@hidden>  wrote on 02/11/2009 20:47:34:
>>>>> On 11/02/2009 03:40 PM, address@hidden wrote:
>>>>>> This series adds support for live migration without shared storage,
>>>> means
>>>>>> copy the storage while migrating. It was tested with KVM. Supports 2
>>>> ways
>>>>>> to replicate the storage during migration:
>>>>>> 1. Complete copy of storage to destination
>>>>>> 2. Assuming the storage is cow based, copy only the allocated
>>>>>> data, time of the migration will be linear with the amount of allocated
>>>>>> data (user responsibility to verify that the same backend file reside
>>>>>> on src and destination).
>>>>>> Live migration will work as follows:
>>>>>> (qemu) migrate -d tcp:0:4444 # for ordinary live migration
>>>>>> (qemu) migrate -d blk tcp:0:4444 # for live migration with
>>>>> complete storage copy
>>>>>> (qemu) migrate -d blk inc tcp:0:4444 # for live migration with
>>>>> incremental storage copy, storage is cow based.
>>>>> I'd like to see the syntax generalized.  For one, the guest may have
>>>>> several disks; an install image cdrom might be available as an nfs image
>>>>> but the main storage is local.  Secondly, there can be several levels of
>>>>> cow and we want to control which one we copy.
>>>>> I'll leave the exact details to the qpeople, but if we can specify a
>>>>> copy depth for each device, where 0=copy nothing, n=copy everything,
>>>>> 1=copy the last level (equivalent to -d blk inc) I think we'll have
>>>>> covered everything.
>>>> I propose the following syntax:
>>>> migrate [-d] [-b [<device:copy_level>  ...<device:copy_level>]]
>>>> tcp:<host>:<port>
>>>> Where device will be the name of the device: ide0-hd0. And copy_level
>>>> will
>>>> be integer or n, 0=flat copy of the device, 1=copy the last level ...
>>>> n=copy all levels.
>>>> All HD devices that will not appear in the command will be treated as
>>>> copy_level=0. All devices != BDRV_TYPE_HD will be ignored.
>>> Looks good.
>> Do I get this correctly: this series is now "only" blocked by the
>> required rework of its user interface? Is there a schedule for this, a
>> v6 roll out? Will it be in time for qemu-0.12?
>> Jan
> It was committed to the master branch a week ago.

Oh, indeed, thanks. Due to the fact that this discussion suggested that
there are still open issues, I did not even checked git. And the missing
merge notifications contributed to this as well.

Anyway, good to see this upstream. /me goes testing.


Siemens AG, Corporate Technology, CT T DE IT 1
Corporate Competence Center Embedded Linux

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