Image mode thin-provisioned volumes

When you create an image mode volume, you can designate it as thin-provisioned. An image mode thin-provisioned volume has a virtual capacity and a real capacity.

An image mode thin-provisioned volume has a direct relationship with a single MDisk where the contents of the MDisk map to the real capacity that is used by the thin-provisioned volume. Unlike fully allocated volumes, the logical block address (LBA) on the MDisk is not necessarily the same as the LBA on the volume. You cannot change the real capacity of an image mode thin-provisioned volume manually or by using the autoexpand feature. To use the autoexpand feature, the volume must be in managed mode.

An image mode thin-provisioned volume might go offline due to insufficient space if new write operations from a host require a change to the real capacity of the volume. Before you start to migrate a thin-provisioned volume to image mode, ensure that enough free capacity is available for the volume for ongoing write operations.

You can use an image mode volume to move a thin-provisioned volume between two systems by using the following procedure. The procedure is similar to the procedure that is used for fully allocated volumes, but has an extra step during the import process to specify the existing thin-provisioned metadata, rather than to create a new, empty volume.

If the volume is not already in image mode, migrate the volume to image mode and wait for the migration to complete.
Delete the volume from the exporting system.
Disconnect the MDisk from the exporting system and connect the MDisk to the importing system.
Create an image mode thin-provisioned volume that uses the MDisk. You must specify the import option.
Migrate the volume to managed mode.

The import option is valid only for thin-provisioned volumes that were created on the system. If you use this method to import a thin-provisioned volume that is created by RAID storage systems into a clustered system, the system cannot detect it as a thin-provisioned volume. However, you can use the volume mirroring feature to convert an image-mode fully allocated volume to a thin-provisioned volume.