Wido den Hollander created CLOUDSTACK-8104:
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Summary: Add TRIM/Discard support to Qemu
Key: CLOUDSTACK-8104
URL: https://issues.apache.org/jira/browse/CLOUDSTACK-8104
Project: CloudStack
Issue Type: New Feature
Security Level: Public (Anyone can view this level - this is the default.)
Components: KVM
Reporter: Wido den Hollander
Assignee: Wido den Hollander
Priority: Minor
Thinly provisioned volumes on storage devices continue to grow because the
storage device has no idea of which blocks are in use.
For SSDs the TRIM/Discard feature was invented to give free/unused blocks back
to the flash device, but this can also be used for Qemu.
Ceph's RBD for example supports trimming so that volumes can shrink again when
blocks are no longer in use.
This is supported since Qemu 1.5, but since 1.6 it also works for QCOW2 images.
It however requires the new virtio-scsi to work optimal, so it requires some
changes.
For more information see:
* http://wiki.qemu.org/ChangeLog/1.5#Block_devices
* http://wiki.qemu.org/ChangeLog/1.6#Block_devices
* http://ceph.com/docs/master/rbd/qemu-rbd/#enabling-discard-trim
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