On 26/08/2019 08:55, Teckelmann, Ralf, NMU-OIP wrote:
Hi Florian,
Thanks for moving our conversation to the mailing list.
From the discussion on the ceph-mailing list I take (as of today):
- Ephemeral boot, *without* RBD, with or without attached volumes: freeze/thaw if hw_qemu_guest_agent=yes, resulting in consistent snapshots.
- Ephemeral boot *from* RBD, also with or without attached volumes: no freeze/thaw, resulting in potentially inconsistent snapshots even with hw_qemu_guest_agent=yes.
- Boot-from-volume from RBD: freeze/thaw if hw_qemu_guest_agent=yes, resulting in consistent snapshots.
One may note that " hw_qemu_guest_agent=yes" stands for - the metadata property set on an image and as well - assumes one does install the qemu-guest agent in that image or on the instances spawned from that image. Besides that, Florian explains further down why os_require_quiesce=yes is very nice to have set as well.
Right, also note that due to the fact that RBD-backed ephemeral images currently bypass quiescing altogether, os_require_quiesce is actually silently ignored for VMs that are RBD-backed AND do not boot from volume. A Nova bug about this is open, and a discussion on how to best fix it is currently ongoing: https://bugs.launchpad.net/nova/+bug/1841160 Cheers, Florian