On 04/06/2012 09:19 AM, Paolo Bonzini wrote: > Il 06/04/2012 06:36, Eric Blake ha scritto: >> if >> 'block_job_cancel' were made part of 'transaction', you could >> copy multiple disks at the same point in time without pausing >> the domain. > > This is doable. > > The transactioned command would do a qemu_aio_flush() in the prepare > phase, and a normal block_job_cancel in the commit phase. > >> This also implies we may want to add a --quiesce >> flag to the pivot operation, so that when breaking a mirror, the >> side of the mirror that we are abandoning is at least in a stable >> state with regards to guest I/O. > > I don't think this is needed. Either it makes a difference so it should > be the default, or it doesn't and then it is not a useful knob. I'm talking about the guest agent. It may make a difference, but cannot be the default, because you cannot trust the guest agent to be present. I'm thinking this will be like the --quiesce operation of snapshot-create, as another situation where the guest agent quiesce can usefully surround a 'transaction' command to improve the results, but must not be default. -- Eric Blake eblake@xxxxxxxxxx +1-919-301-3266 Libvirt virtualization library http://libvirt.org
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