Claiming Unallocated Space on RAID Array

Posted on 2014-02-27
Medium Priority
Last Modified: 2016-12-08

On an SBS 2008 server, I have a RAID 5 array of 4 1TB disks so the usable space is 3 TB.  The drive shows my 100GB Drive C partition, 2TB Drive D partition, and 756 Unallocated space.  I want to use the 745 unallocated but Disk Management doesn't give me an option to create any volumes, they are all greyed out.

I realize MBR formatted volumes can only be 2 TB but why can't I have an additional volume here.  We need the storage space and it's so frustrating seeing it there but unusable.

Is there any way to access it without doing a complete server rebuild?  It's a Dell PowerEdge T310.

Thanks so much for any guidance
Question by:WilMaTech

Accepted Solution

insidetech earned 400 total points
ID: 39891889
Was the RAID 5 build using the hardware controller? And the volumes created as vDisks?

Look at your controller configuration and perhaps all you need to do is create another vDisk using the left over space.
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Assisted Solution

David earned 400 total points
ID: 39891909
You're screwed.  The largest LUN that this controller / system will do is 2TB.  You should then reconfigure to either a single RAID10 (it won't change capacity but will be at least 2x faster overall), or a pair of RAID1s.   If you must have more space, then buy 2 x 2TB drives, and then a 1x1TB RAID1 for boot, then with the 2x2TB make that the other RAID1 giving 3TB total usable.

LVL 10

Assisted Solution

by:Subhashish Laha
Subhashish Laha earned 400 total points
ID: 39891917
Yes, MBR disks size is maximum 2TB. You can create multiple partitions but total disk size should not exceed 2TB.

The only option left is to take backup and rebuild your server with GPT disk to use complete 3TB.

Author Closing Comment

ID: 39892046
Thanks for the confirmation.  The whole GPT thing flew under my radar.  When I added the 4th 1TB drive to the RAID5 array, I expanded the existing virtual disk rather than creating a 2d one (so I did 1-3TB virtual disk vs. 2TB and 1TB).  The server is maxed out on hard drives now and any modifications would be very challenging.  Lesson learned.  Interestingly I looked at my setup and saw wait I have a C: of 97 and D: of 1950 that's more than 2TB.  But when I did the exact math, it ended up being 2048GB total to the penny.  Thanks for the info.
LVL 47

Expert Comment

ID: 39892062
The reason you saw 97GB is because the most significant bit, bit #33 was dropped.  The reason that the limit is 2TB is because the SCSI CDB at the time this was all being designed was a 10 byte command that used 4 bytes for the addressable block number.

So largest addressable block was FFFFFFFD hex blocks which corresponds to 512 bytes x 4,294,967,293 byte offset or roughly 2TB.

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