On Thu, Sep 29, 2016 at 04:43:25PM +0800, Fam Zheng wrote: > On Thu, 09/29 09:34, Daniel P. Berrange wrote: > > I got a report that the LUKS block driver was not working in combination > > with the drive-mirror command and have been investigating possible fixes > > for this. > > > > The core problem here is dealing with the target image. If you try to > > run with a pre-created target that is a LUKS image, it will fail because > > we have no way to provide the "key-secret" option required to open the > > target. If you try to tell drive-mirror to create a new target with > > LUKS format, it will fail trying to create the image, again because > > no "key-secret" option can be provided. > > > > While this is a fundamental blocker problem for LUKS, it also affects > > other image formats. For example, if you're telling drive-mirror to > > create a new qcow2 volume, its impossible to control desirable attributes > > like cluster-size, or compat-level. If you're mirroring a qcow2 file to > > a new qcow2 file, it is impossible to maintain any custom runtimes opts > > yuou might have set on the source - eg 'lazy-refcounts', or the various > > discard settings will all be stuck on defaults for the target. > > > > You can workaround the problem of being able to create new volumes by > > just creating them using qemu-img ahead of time instead. > > > > Dealing with the problem of opening images, requires that we have some > > way to provide block options to the drive-mirror command. The naive > > approach would to just add a new parameter > > > > 'options': ['str'] > > > > but IMHO this is just perpetuating the broken design of drive-mirror. > > > > The core problem is that this command should not have been using a > > plain target + format pair of strings in the first place. Instead it > > should have had a single > > > > "target": "BlockdevOptions" > > > > So my suggestion is that we deprecate "drive-mirror" and define a fixed > > command "drive-mirror-blockdev" (or "blockdev-mirror" ?) that accepts > > the proper BlockdevOptions QAPI type for the target as above. > > Are you aware that there is already a blockdev-mirror command? Supposedly it > can do what you need, together with blockdev-add once the latter is deemed > ready.
Clearly I'm not aware of that :-) It seems libvirt does not yet use blockdev-mirror either, which is where I got the original bug report about drive-mirror from. I'll submit a patch to mark drive-mirror as deprecated and point the otherwise ignorant reader towards blockdev-mirror instead.... Regards, Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://entangle-photo.org -o- http://search.cpan.org/~danberr/ :|
