Ensure that you are familiar with using image mode virtual disks (VDisks).
An image mode VDisk provides a direct block-for-block translation from the managed disk (MDisk) to the VDisk with no virtualization. This mode is intended to allow virtualization of MDisks that already contain data that was written directly, not through a SAN Volume Controller node. Image mode VDisks have a minimum size of 1 block (512 bytes) and always occupy at least one extent.
Image mode MDisks are members of an MDisk group but, they do not contribute to free extents. Image mode VDisks are not affected by the state of the MDisk group because the MDisk group controls image mode VDisks through the VDisks association to an MDisk. Therefore, if an MDisk that is associated with an image mode VDisk is online and the MDisk group of which they are members goes offline, the image mode VDisk remains online. Conversely, the state of an MDisk group is not affected by the state of the image mode VDisks in the group.