##cinder/nova
- live migration cannot work. update: apparently it does work in grizzly
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real live migration will fail as a preflight check that nova does is to test if you are using shared storage for your /var/lib/nova/instances directory (it writes a test file to the shared location on one host, then checks to see if it can see it on the other). Given that RBD is not 'shared storage' in this sense, the check fails. NOT fixed in Havana, though it's noted that ceph and libvirt will play nicely outside of nova
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block migration will fail as there is no actual disk for the process to copy from one host to another
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each compute host needs to be 'manually' configured with the libvirt secret/key when using cephx
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to use RBD, in grizzly, you need to create a volume from a glance image, and then boot from volume with nova. Not dreadful, but not seamless. In Havana https://blueprints.launchpad.net/nova/+spec/bring-rbd-support-libvirt-images-type allows nova to directly use RBD images
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cinder rbd driver uses rbd cli client in grizzly. Uses librbd in havana.
bug: cinder ignores rbd_user in cinder.conf
##glance
-bug: can boot multiple instances from single cinder volume created from a glance image
-bug: no 'volume_image_metadata' population when cloning a glance image, so ciner client sees bootable=false
-set show_image_direct_url=True to get COW clones from glance to cinder
-uses librbd directly
-when not using back end COW cloning, cinder will convert to raw for you before creating the volume. If using COW, it will not so the image needs to be a raw image in glance first.