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

[Avi Kivity <avi@redhat.com>]

On 11/03/2009 11:40 AM, Liran Schour wrote:
> - Liran
>
> Avi Kivity<avi@redhat.com>  wrote on 02/11/2009 20:47:34:
>    
>> On 11/02/2009 03:40 PM, lirans@il.ibm.com 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.

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