nova/releasenotes/notes/cinder-backend-report-discard-1def1c28140def9b.yaml
Patrick East 6bc074587a libvirt: add discard support for attached volumes
If Cinder reports discard=true capability then add
discard=unmap to disk config setting on attached volume.

To have this actually provide unmap/trim support the instance must have
been configured with a controller+bus type that can support it. As of
now the only one known not to work is virtio-blk. In the case where we
detect a configuration that will not work a warning will be logged, but
the attachment will continue with the default behavior.

An example of how to get a controller and bus to support this is to set
the following Glance properties on an image:

hw_scsi_model=virtio-scsi
hw_disk_bus=scsi

This feature also has some requirements for the libvirt and qemu
versions being used. There is a check to ensure that libvirt is at least
1.0.6 and qemu is at least 1.6.0. If the minimum versions are not met
a warning will be logged, but the attachment will continue with the
default behavior.

Change-Id: Icd2d20bb6906d9106df34a970b3d81b17bc3ec07
Implements: bp cinder-backend-report-discard
2016-01-08 13:07:36 -08:00

10 lines
447 B
YAML

---
features:
- Add support for enabling discard support for block devices with libvirt.
This will be enabled for Cinder volume attachments that specify support
for the feature in their connection properties. This requires support to
be present in the version of libvirt (v1.0.6+) and qemu (v1.6.0+) used
along with the configured virtual drivers for the instance. The
virtio-blk driver does not support this functionality.