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

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

[lirans]

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

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

[Pierre Riteau]

On 10 sept. 2009, at 12:26, 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.
>
> 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/

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

[Liran Schour]

qemu-devel-bounces+lirans=il.ibm.com@nongnu.org wrote on 10/09/2009
17:35:53:

> On 10 sept. 2009, at 12:26, 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.
> >
> > 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).

It seems that there is a memory leak but from what I see it is a memory
leak in
raw_aio_writev. Seems like bdrv_aio_writev does not call the callback on
completion.
Therefore the buffer allocated for the aio_writev is not being freed.
Anyone knows
about this bug?

- Liran

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

[Jan Kiszka]

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.
> 
> The patches are against git://git.kernel.org/pub/scm/virt/kvm/qemu-kvm.git 
> kvm-87

As you are posting to qemu-devel, you should base your work on top of
qemu.git master and make sure that it still works as intended. Upstream
has KVM support (that is normally even usable), so testing won't take
much longer than with qemu-kvm.

Nice feature by the way! Are you (also) using it to generate backups of
a VM without stopping it (for a noticeably long time)? That's what we
have in mind ATM.

Jan

-- 
Siemens AG, Corporate Technology, CT SE 2
Corporate Competence Center Embedded Linux

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

[Liran Schour]

qemu-devel-bounces+lirans=il.ibm.com@nongnu.org wrote on 11/09/2009
14:25:29:

> 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.
> >
> > The patches are against
git://git.kernel.org/pub/scm/virt/kvm/qemu-kvm.git
> > kvm-87
>
> As you are posting to qemu-devel, you should base your work on top of
> qemu.git master and make sure that it still works as intended. Upstream
> has KVM support (that is normally even usable), so testing won't take
> much longer than with qemu-kvm.
>
I will post a patch based on qemu.git.

> Nice feature by the way! Are you (also) using it to generate backups of
> a VM without stopping it (for a noticeably long time)? That's what we
> have in mind ATM.
>
Right now I am not using it for different scenario accept live migration.
But it
can be done easily.

- Liran