Repartitioning and converting large array to GPT disk

Posted on 2009-05-18
Last Modified: 2013-12-01
I have a server at a client with a six-drive RAID 5 array that was recently upgraded from 250GB disks to 1TB disks.  The server was--for various reasons--configured during its initial install years ago with a single partition (C:) for both the OS and data partitions.  A Dell PERC/5i running firmware version 5.0.2-0003 handles the array and there a single virtual disk on the controller formatted as a MBR disk.

Long story short, I need to find some way to convert the disk to GPT so I can access the entire 4TB (one drive is a hot spare) of usable space through a single drive letter.  I realize this can't be done on an active OS partition.  I'm not against splitting the OS and data into separate partitions, but I'm looking for advice on how to do this without backing up the entire server and doing a fresh install with brand new partitions.  Perhaps there is some way to use the PERC management tools to split off some of the physical disks from the existing array into new virtual disks without losing any existing data?  Any ideas would be appreciated, thanks!

Question by:flux303
LVL 88

Accepted Solution

rindi earned 500 total points
ID: 24419288
As you have already mentioned, you can't go to 4TB on the active system partition. So I suggest leave your System partition at it's current size and create one or more additional partitions from the extra space, then move all data from C to the new partitions.

I must also stress that a good backup is always necessary, whether you do any system changes or not. So if the customer hasn't been backing up I would refuse to touch the server, or get him to sign a paper where you aren't liable to account for any data that may get lost during the process. Get him to get a good DR plan in place. Things can go wrong during normal operation, as well as when you do any changes.

If all that is cleared up, and if the raid controller has an "expand" function (most good raid controllers used in servers have that function, but recheck the controller's manual and if possible confirm this with Dell), then you should be able exchange each HD one by one, always waiting until the new disk has finished syncing and is OK before changing the next HD. Once all disks have been replaced with the new, larger ones, and the array is healthy, use the Controller's utility to expand the array so it's full size can be used. This is usually a quick change. After that (you will need to reboot), your server's diskmanagement should show the new unpartitioned empty, available space. This you can now assign a partition/partitions to and assign them drive-letters for use for your data.

All this shouldn't touch your data, but as I mentioned, things can always go wrong, and for that you really should have a verified good backup.
LVL 46

Expert Comment

ID: 24419335
flux303, it is impossible to convert the drive into Guid Partitioning Table format without deleting existing partition on the array.
PERC management tools does not allow selecting dynamic\GPT or basic types of partitioning as far as I know.
Backup your data and reinstall the OS + applications to GPT partitioned drive of 4TB.
LVL 46

Expert Comment

ID: 24419352
rindi, I don't think he will be able to expand the drives due to MBR partitioning limitation of 2048GB size.
Windows will not work with space that exceeds this limit on MBR disks, that's why Microsoft added this GPT partitioning format.
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LVL 88

Expert Comment

ID: 24419384
At the moment his windows partition is smaller than 2TB. Expanding the array itself should be no problem using the raid controller. He just can't get a partition larger than 2TB for his windows partition, and I don't recommend that anyway. He should rather build separate partitions from his newly gained space.
LVL 46

Expert Comment

ID: 24419496
He could not build new partitions on new space again due to 2TB limit of MBR. He can create additional partitions inside of 2048GB zone not out of it. Even if he manage to create new partitions out of 2TB zone Windows will not work with them if the drive is MBR type.

Expert Comment

ID: 24647601
If you can move the system files to a separate disk (not just a separate partition) somehow, then you can use gptgen ( - open-source tool) to convert the drive "on-the-fly" (with data on it) to GPT. I don't recommend trying this with the boot files on the disk being converted, as gptgen doesn't handle boot partitions itself (though it may be possible to restore bootability of the partition after converting the disk to GPT, I haven't tested this situation.

Author Closing Comment

ID: 31582731
Thanks to all, I spoke with Dell and the only option to create new virtual disks on the PERC is to wipe the existing containers, build from scratch, and bare metal restore OS and Data to new VDs.  Awarding points to rindi for quick & comprehensive response.

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