Re: [Qemu-devel] [RFC PATCH v3 06/11] qemu-ga: Add Windows VSS requester to quisce applications and filesystems

[Eric Blake]

On 05/21/2013 09:33 AM, Tomoki Sekiyama wrote:
> Add VSS requester functions for to qemu-ga.
> This provides facility to request VSS service in Windows guest to quisce

s/quisce/quiesce/

> applications and filesystems. This function is only supported in Windows
> 2003 or later. In older guests, this function does nothing.
> 
> In several versions of Windows which don't support attribute
> VSS_VOLSNAP_ATTR_NO_AUTORECOVERY, DoSnapshotSet fails with error
> VSS_E_OBJECT_NOT_FOUND. In this patch, we just ignore this error.
> To solve this fundamentally, we need a framework to handle mount writable
> snapshot on guests, which is required by VSS auto-recovery feature
> (a cleanup phase after snapshot is taken).

I take it that such a framework may involve additional guest-agent
commands and management work (such as libvirt having to be aware of the
added framework).  How important is this functionality?  How frequently
does VSS even get us into that state?  That is, are Windows guests going
to frequently hit our current first-round implementation limits that
fail to let them do auto-recovery?

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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