I took a server at work to test stuff a bit further, although our 3PAR isn't up til' tomorrow so was only able to provision LUNs from our existing storage.
Basically it seems pretty straight forward in terms of DPM (there's tons of considerations elsewhere with sanboot and all).
I did find the initial hint from the DPM-group pretty clever, I like that the migration is being done in such low-level and that you won't get any distruptions at all.
But converting all 30 servers disks from basic to dynamic as well as having a 2 TB drive with critical data in a "sync"-state... it sort of feels a bit more risky.
Consideration 1; The changejournal which DPM activates when protecting a volume will not retain the same USN when a file is simply copied (like robocopy) even if driveletters are 'swapped' so a full backup will be performed.
Solution: VSS-aware application such as DriveImage XML can do live copying without causing the changelog to update the sequence number for a file. It's awfully slow though. don't know if its the vss-lock or the specific application here
that makes it slow.
An 'offline' disk-to-disk copy performed via WinPE is much faster (a free but proprietary backup/restore application) and will also retain the journal.
Only drawback is that we can't speed up migration by pre-copying everything before maintanence window and do a final mirroring (robocopy /MIR),
Consideration 2: DPM binds its protected source to a protected member's volume GUID (not the driveletter). Cloning a disk/partition at the protected member will effectively result in Windows giving the new disk a unique volume guid, since
a disk has a unique serialnumber, and this in turn will result in a unique hex checksum as seen in HKLM\system\mounteddevices.
After cloning, an error occurs in DPM during recoverypoint saying <volume guid> is missing at protected member
solution: The script 'migrate-datasource.ps1' which is located and shipped in the dpm-servers installdir takes care of this just fine.
Any corrections, suggestions or whatnot input is welc