SAN volume configuration options

You must set various options on the volume containing your LUN. The way you set the volume options determines the amount of space available to LUNs in the volume.

Autogrow

You can enable or disable Autogrow. If you enable it, autogrow allows ONTAP to automatically increase the size of the volume up to a maximum size that you predetermine. There must be space available in the containing aggregate to support the automatic growth of the volume. Therefore, if you enable autogrow, you must monitor the free space in the containing aggregate and add more when needed.

Autogrow cannot be triggered to support Snapshot creation. If you attempt to create a Snapshot copy and there is insufficient space on the volume, the Snapshot creation fails, even with autogrow enabled.

If autogrow is disabled, the size of your volume will remain the same.

Autoshrink

You can enable or disable Autoshrink. If you enable it, autoshrink allows ONTAP to automatically decrease the overall size of a volume when the amount of space consumed in the volume decreases a predetermined threshold. This increases storage efficiency by triggering volumes to automatically release unused free space.

Snapshot autodelete

Snapshot autodelete automatically deletes Snapshot copies when one of the following occurs:

You can configure Snapshot autodelete to delete Snapshot copies from oldest to newest or from newest to oldest. Snapshot autodelete does not delete Snapshot copies that are linked to Snapshot copies in cloned volumes or LUNs.

If your volume needs additional space and you have enabled both autogrow and Snapshot autodelete, by default, ONTAP attempts to acquire the needed space by triggering autogrow first. If enough space is not acquired through autogrow, then Snapshot autodelete is triggered.

Snapshot reserve

Snapshot reserve defines the amount of space in the volume reserved for Snapshot copies. Space allocated to Snapshot reserve cannot be used for any other purpose. If all of the space allocated for Snapshot reserve is used, then Snapshot copies begin to consume additional space on the volume.