Re: [Qemu-devel] Re: [PATCH 0/3 v3] Live migration without shared storage

[Liran Schour]

Kevin Wolf <address@hidden> wrote on 17/09/2009 18:38:59:

> Am 17.09.2009 16:03, schrieb Jan Kiszka:
> > 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
ofallocated
> >>     data (user responsibility to verify that the same backend file
reside
> >>     on src and destination).
> >
> > For my understanding: Does it require the use of qcow[2] or does it
also
> > work with raw images?
>
> This leads me to the question what the block migration is doing with
> qcow2 images (or better: images in any format but raw). What happens
> with non-standard image options (like cluster size)? Are snapshots
> copied over or won't they be available any more on the destination host?
>

For now the block migration will only copy data. 2 ways for replicating the
data:
-b means copy all data to the destination, image on the destination can be
in a
different format from source but all blocks will be written.
-i means copy only allocated data, only the data that is allocated and
valid will
be copied (I use bdrv_is_allocated() to figure out what to copy). Base
image should
be identical on source and target. No snapshot or any kind of metadata will
be copied,
snapshots will be lost on this case.
It is possible to replicate snapshots data also but I did not implement
that for now.

- Liran