246 Implementing the IBM Storwize V7000 with IBM Spectrum Virtualize V8.2.1
Image mode creates one-to-one mapping of logical block addresses (LBAs) between a 
volume and an MDisk (LU presented by the virtualized storage). Image mode volumes have 
the minimum size of one block (512 bytes) and always occupy at least one extent. An Image 
mode MDisk cannot be used as a quorum disk and no IBM Spectrum Virtualize system 
metadata extents are allocated from it; however, all of the IBM Spectrum Virtualize copy 
services functions can be applied to image mode disks. The difference between a managed 
mode volume (with striped extent allocation) and an image mode volume is shown in 
Figure 7-4.
Figure 7-4   Image mode volume versus striped volume
An image mode volume is mapped to one, and only one, image mode MDisks and is mapped 
to the entirety of the MDisk. Therefore, the image mode volume capacity must be equal to the 
size of the corresponding image mode MDisk. If the size of the (image mode) MDisk is not a 
multiple of the MDisk group’s extent size, the last extent is marked as partial (not filled).
When you create an image mode volume, the specified MDisk must be in unmanaged mode 
and must not be a member of a storage pool. As the image mode volume is configured, the 
MDisk is made a member of the specified storage pool (Storage Pool_IMG_xxx).
IBM Spectrum Virtualize also supports the reverse process, in which a managed mode 
volume can be migrated to an image mode volume. The extent size that is chosen for this 
specific storage pool must be the same as the extent size of the storage pool into which you 
plan to migrate the data off the image mode volumes. If a volume is migrated to another 
MDisk, it is represented as being in managed mode during the migration. Its mode changes to 
“image” only after the process completes.
It is a preferred practice to put image mode MDisks in a dedicated storage pool and use 
a special name for it (for example, Storage Pool_IMG_xxx).