I've got to say, the migration...was very smooth. I inserted the drive, then did everything from the Dell OpenManage software (GUI through a browser window). I converted it to a RAID-capable disk, then reconfigured the virtual volume to a RAID 5 and added the new disk in a single operation with easy to use, mostly-labeled multi-step screens (one or two boxes could have been a little more clearly described).

Sure, the process took around 25-28 hours to complete, but that's not too surprising. After it was finished, Windows still didn't see the expanded volume, so I had to re-scan the drives in Disk Management. Then I had to increase the partition size which I did with MiniTool Partition Wizard, which has always worked well for me.

Despite several ways this could have gone badly, it seems to be fine.

I only have two remaining question points:

1) Am I maxed out? Does Windows server limit virtual volumes the same way as physical disks? I assume the answer is yes. If so, I was able to determine that this system uses BIOS so it seems I'm maxed at 2TB unless I rebuild the OS.

2) I'm a little puzzled about the storage I'm left with. The new volume appears to have 1.04TB of data on it. This is on Sunday, when the upgrade finished last night. There's no way it could have had that much data on it on Thursday. And I just looked again and it appears to be growing. Any thoughts on a good way to figure out where the data is being added?