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Forum Discussion
X-RAID Volume Smaller than expected
This is not a big deal, but it puzzles me, so I thought I would ask if anyone has an explanation. My RN214 was configured with 2x8 TB + 2x1.5 TB drives, and it reported a total volume size of 9.9...
Mauser69 wrote:Looking closer at the Admin Page Volumes screen, the NAS reports these capacites for each drive: 7.3 + 7.3 + 2.7 + 2.7.
Thus, using the actual capacities reported by the NAS, a total of 20 TB - 7.3 TB = expected volume size of 12.7 TB. So why is there 1.3 TB missing?
8TB drives are decimal so effective 7.3TB resp. 3TB are effectively 2.7TB. They sell you 1TB ==1.000.000.000.000 B (and not 1.099.511.627.776 B) As two of each are in a RAID1 it's 7.3TB+2.7TB or about 11TB effectively available - minus file system overhead.
Mauser69 wrote:And I also assumed that if I upgraded the smaller drives, I would gain 100% of the new capacity in
As I said above, I THOUGHT that as long as my largest drive did not change, I would gain 100% of the new drive space in the total volume size?
And where should the RAID redundancy come from for the added devices?
"As two of each are in a RAID1 it's 7.3TB+2.7TB or about 11TB effectively available - minus file system overhead."
Actually, I do not think that is correct, at least as far as I understand the manual. And the Admin Page, System | Volumes tab, specifically reports that this volume is X-RAID, RAID 5 (not RAID 1).
Furthermore, since the whole volume is RAID 5, with one of the largest drives reserved for the redundancy of the entire volume, no ADDITIONAL redundancy space would be needed for any increase in the size of the smaller drives.
The capacity rule is "sum the drives and subtract the largest". In your case, the adds up to 14 TB. The NAS displays TIB though, and that does work out to 12.73 TiB.
But you can't upgrade the 1.5 TB drives to 3 TB drives with XRAID. You can replace drives, or upgrade drives to the largest size in the array (or larger). But (apart from some rare exceptions) you can't upgrade a smaller drive to an intermediate size. That was why the space didn't change.
Mauser69 wrote:
Actually, I do not think that is correct, at least as far as I understand the manual. And the Admin Page, System | Volumes tab, specifically reports that this volume is X-RAID, RAID 5 (not RAID 1).
What you have was a volume comprised of 2 RAID groups -
- a 4 x 1.5 TB RAID-5 group (slightly smaller, but close enough).
- a 2 x 6.5 TB RAID-1 group
These were concatenated together into the single volume.
Note each group is a partition on the drives. So there are two data partitions on the 8 TB drives.
The reason the upgrade to 3 TB didn't work is that the system would have had to repartition the 6.5 partition on the 8 TB drives. XRAID won't do that.
If you want all the extra space, you'll need to re-create the volume and restore the files from backup.
StephenB wrote:But you can't upgrade the 1.5 TB drives to 3 TB drives with XRAID. You can replace drives, or upgrade drives to the largest size in the array (or larger). But (apart from some rare exceptions) you can't upgrade a smaller drive to an intermediate size. That was why the space didn't change.
The reason the upgrade to 3 TB didn't work is that the system would have had to repartition the 6.5 partition on the 8 TB drives. XRAID won't do that.
If you want all the extra space, you'll need to re-create the volume and restore the files from backup.
Actually, the drive upgrade from 1.5 TB to 3 TB drives DID work just fine, and the total volume space DID increase, just not by quite as much as I expected (I added 3 TB total, but the volume size only increased by 1.4 TB).
I suspected that if I started over fresh with the 4 current drives, maybe the system would find the missing space (but I did not know why - it was just a guess). However, since the missing 1.3 TB of space is quite small in comparison to the entire volume of 11.3 TB, it is really not worth the work to try and start over again. But I'll remember that possibility if I try to vertically expand the volume again in the future.
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