Image mode volumes

An image mode volume provides a direct block-for-block translation from the managed disk (MDisk) to the volume with no virtualization.

This mode is intended to provide virtualization of MDisks that already contain data that was written directly, not through a IBM Spectrum Virtualize™ node. Image mode volumes have a minimum size of 1 block (512 bytes) and always occupy at least one extent.

Image mode MDisks are members of a storage pool, but they do not contribute to free extents. Image mode volumes are not affected by the state of the storage pool because the storage pool controls image mode volumes through the association of the volume to an MDisk. Therefore, if an MDisk that is associated with an image mode volume is online and the storage pool of which they are members goes offline, the image mode volume remains online. Conversely, the state of a storage pool is not affected by the state of the image mode volumes in the storage pool.

An image mode volume behaves just as a managed mode volume in terms of the Metro Mirror, Global Mirror, and FlashCopy® Copy Services. Image mode volumes are different from managed mode in two ways:

Migration. An image mode volume can be migrated to another image mode volume. It becomes managed while the migration is ongoing, but returns to image mode when the migration is complete.
Quorum disks. Image mode volumes cannot be quorum disks. This means that a clustered system with only image mode volumes does not have a quorum disk.

Remember: You cannot resize (expand or shrink) an image mode volume.