How to Enable 'Discard/TRIM' in Openstack Instance ?

Problem

• How do I enable TRIM (Discard) in a OpenStack KVM instance?

Environment

• Platform9 Managed OpenStack - v5.4 and Higher

Cause

• The default disk driver for KVM images is virtio. This driver does not supports / implements the fitrim IOCTL. Thus, it is needed to use virtio-scsi, which supports FITRIM.

Resolution

• Create or modify a glance image adding the virtio-scsi disk bus property:

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# glance image-update --property hw_scsi_model=virtio-scsi --property hw_disk_bus=scsi <image>

Or

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# openstack image set --property hw_scsi_model=virtio-scsi --property hw_disk_bus=scsi <image>