Re: [Qemu-devel] [PATCH 0/3] Live migration without shared storage (improved version)

[Pierre Riteau]

On 10 sept. 2009, at 12:26, 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.
>
> The patches are against git://git.kernel.org/pub/scm/virt/kvm/qemu-kvm.git
> kvm-87


Just tried with the v2 of the third patch. Now throughput is much  
better when the disk image has already been allocated (zero'd with dd)  
on the receiving end.

However, you must have a memory leak somewhere: at the end of the  
migration of a 128MB VM, the destination machine was swapping and qemu  
was using nearly 2GB of resident memory (the size of the disk image  
was 2GB).

--
Pierre Riteau -- http://perso.univ-rennes1.fr/pierre.riteau/