On Tue, Apr 21, 2015 at 05:28:01PM +0200, Paolo Bonzini wrote: > On 21/04/2015 03:25, Wen Congyang wrote: > >> > Please do not introduce "<name>+colo" block drivers. This approach is > >> > invasive and makes block replication specific to only a few block > >> > drivers, e.g. NBD or qcow2. > > NBD is used to connect to secondary qemu, so it must be used. But the > > primary > > qemu uses quorum, so the primary disk can be any format. > > The secondary disk is nbd target, and it can also be any format. The cache > > disk(active disk/hidden disk) is an empty disk, and it is created before run > > COLO. The cache disk format is qcow2 now. In theory, it can be ant format > > which > > supports backing file. But the driver should be updated to support colo > > mode. > > > > > A cleaner approach is a QMP command or -drive options that work for any > > > BlockDriverState. > > > > OK, I will add a new drive option to avoid use "<name>+colo". > > Actually I liked the "foo+colo" names. > > These are just internal details of the implementations and the > primary/secondary disks actually can be any format. > > Stefan, what was your worry with the +colo block drivers?
Why does NBD need to know about COLO? It should be possible to use iSCSI or other protocols too. Stefan
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