Procedure for Migration and Cutover of Windows Storage Services Virtual Disks of a Storage Pool

Note: Throughout this procedure, ensure the legacy Disk Manager tool of Computer Manger is NOT running. Use only the Sever Manager's "File and Storage Services" tool to perform the below steps. For Remote Migration (Host to Host), make sure Disk Manager tool is not running on both hosts.

For each Source Virtual Disk created using a Storage Pool, create a Destination Virtual Disk (must be exactly the same size) from a Storage Pool. The Destination Virtual Disk should not have any volume created. If a volume was already created, right-click and click "Reset Disk" to erase the disk. Then, the disk should be taken offline by right-click on the disk and click "Take Offline". The disk should be kept at this state until the very last step of the cutover.

Create a Migration Session after pairing the Source and Destination Virtual Disks.

When the initial sync of the disk is complete (100%), the status becomes "Tracking Changes". It is ready for the next step for cutover. At this point, the Source Disks are not yet masked, and the Destination Disks are masked, indicated by an “Unknown” Partition Type.

To start the cutover process, at the "File and Storage Services" tool, offline the Source Disk by Right-click and select "Take Offline". This will trigger final flush of pending writes cached by Windows Storage.

At CMC Project->Migration Session page, use the red "SESSION ACTIONS" button to "Trigger cMotion". I/O at the source is now redirected to the Destination Disks. Both the Source and Destination Disk are masked, but source continues to be accessible through redirection to the destination.

Use "SESSION ACTIONS" button to trigger "Finalize Cutover". This will unmask (descramble) the Destination Disks. But the Destination Disks at this point are still offline.

At CMC Migration Session page, delete the Migration Session. This will cut off the redirection so that the Source and Destination are no longer linked. The Destination Disks are now independent of the Source, and can be brought online.

At "File and Storage Services" tool, right-click on each Destination Disk and "Bring Online". If you get a warning that the disk is already online on another server (for remote migration from host to host) click Yes to continue. Perform a Rescan using the TASKS menu on top-right. The migrated volume should become visible.

Note: After the above migration and cutover procedure, the Destination Disks are unmasked and visible for production use. The Source Disks are masked and no longer appear to have a partition (became “Unknown”). The data is still on the disk. If you wish to access the disks, contact support for procedure to re-signature the disks with a set of new UUID and to unmask the disks.
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