Public bug reported:
[ Impact ]
Ceph performs much better when I/O is 4k-aligned otherwise it has to
read the 4k from disk, modify and write it again. Linux guests generally
submit 4k-aligned I/O, however Windows guests generally submit
512b-aligned I/O. This can lead to significantly degraded performance
for Openstack Windows guests when using the Ceph RBD backend.
This SRU backports upstream patches[0-2] which enable hinting the
logical block size of cinder devices to Nova and which in turn allows
the Windows guest to perform 4k-aligned I/O.
[ Test Plan ]
1. Deploy openstack with cinder enabled and the ceph backend
2. Create a new volume and ensure that the blocksize is not passed to
libvirt
3. Create a new volume with the disk_geometry option and ensure that the
block size is properly passed to libvirt
[ Where problems could occur ]
* Virtual disks may not support setting block size [0]. As a result, setting
the disk_geometry on LUN drives may cause errors in Nova. This is mitigated by
leaving the disk_geometry option unset by default and allowing users to opt in
on a driver by driver basis.
* This has already been surfaced and addressed by the second patch of the
series [2].
[ Other Info ]
* As noted in [0], for existing volumes, the libvirt xml will need to be
regenerated for the effects to be seen e.g., by reattaching the volume. See the
release-notes for the patch [1] for more details.
* A corollary of the above, after some discussion with @mruffell, its
probably best to backport this to interim releases as well as LTS, to minimize
the number of times this detach/re-attach process needs to be carried out.
[0]: https://bugs.launchpad.net/bugs/2127196
[1]: https://review.opendev.org/c/openstack/cinder/+/658283
[2]: https://review.opendev.org/c/openstack/cinder/+/975540
** Affects: cloud-archive
Importance: Undecided
Status: New
** Affects: cloud-archive/antelope
Importance: Undecided
Status: New
** Affects: cloud-archive/bobcat
Importance: Undecided
Status: New
** Affects: cloud-archive/caracal
Importance: Undecided
Status: New
** Affects: cloud-archive/dalmatian
Importance: Undecided
Status: New
** Affects: cloud-archive/epoxy
Importance: Undecided
Status: New
** Affects: cloud-archive/flamingo
Importance: Undecided
Status: New
** Affects: cloud-archive/yoga
Importance: Undecided
Status: New
** Affects: cloud-archive/zed
Importance: Undecided
Status: New
** Affects: cinder (Ubuntu)
Importance: Undecided
Assignee: Zachary Raines (raineszm)
Status: New
** Affects: cinder (Ubuntu Jammy)
Importance: Undecided
Status: New
** Affects: cinder (Ubuntu Noble)
Importance: Undecided
Status: New
** Also affects: cinder (Ubuntu Noble)
Importance: Undecided
Status: New
** Also affects: cinder (Ubuntu Jammy)
Importance: Undecided
Status: New
** Also affects: cloud-archive
Importance: Undecided
Status: New
** Also affects: cloud-archive/caracal
Importance: Undecided
Status: New
** Also affects: cloud-archive/flamingo
Importance: Undecided
Status: New
** Also affects: cloud-archive/yoga
Importance: Undecided
Status: New
** Also affects: cloud-archive/epoxy
Importance: Undecided
Status: New
** Also affects: cloud-archive/zed
Importance: Undecided
Status: New
** Also affects: cloud-archive/bobcat
Importance: Undecided
Status: New
** Also affects: cloud-archive/dalmatian
Importance: Undecided
Status: New
** Also affects: cloud-archive/antelope
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/2165345
Title:
[SRU] Allow 4k aligned IO for windows guests
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