Expanding RAID - failing

[peteophoven]

Dear Community.

We have begun expanding the volume from 1.8 TB with three 1TB drives running in RAID X2.

We purchased 3 x 4TB drives.  

The first 2 added just fine.  Taking us to 6.4TB.  

I am trying to expand the volume for the third time and it keeps failing with no information.  Only, Error expanding volume.

Does anyone have any suggestions?  

I know there is a hard limit at 1.8TB + 8TB on older models.  But we aren't hitting that threshold.  

If we add the last 4TB drive - 3277 GB plus the redundancy with the raid, we will be adding about 2.668 TB taking us to exactly 9TB.

Does anyone have any leads or where I should look or try?  

I can reinstall the firmware, but cannot take it to factory - this is the production server.  

Thanks for your help and feedback.

Pete

[StephenB · Accepted solution]

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@peteophoven wrote:

We started the volume with 3 X 1 TB drives.

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OK.  That's the same volume size as a single 2 TB drive (except you have redundancy).

Because your starting point was 1.8 TiB, your volume expansion ceiling is 9.8 TiB.

3x1TB + 3x4TB would give you a volume size of 11 TB (or 10 TiB),

The last drive expansion still fails because it would take you over your expansion ceiling (just barely, but still over).

Reformatting the drive won't overcome that.  As I said above, you either need to do off-line expansion with ssh, or do a factory reset and restore the data from backup.

If you do a factory reset, you can switch to OS-6.  Though not supported by Netgear, it doesn't have any known expansion limits.

[StephenB]

What firmware are you running?  I ask because of the "OS 6 on Legacy" tag on your post.  That implies OS-6, but your post suggests something else.

Your 9 TB expectation isn't right - In your case you should end up at 8 TB total volume size (7.3 TiB).

That shouldn't be hitting any expansion limits with OS 4.2.

BTW, 2x4TB+2TB should have given you ~5.4 TiB  Are you seeing 6.4 TiB now?

[peteophoven]

Thank you.

Yes to clarify it is a ReadyNAS Pro 6.

Firmware 4.2.28

Here is how the drives are currently setup:

RAID Level X-RAID2, 6 disks  Showing 6466GB

Status:  Redundant

Ch1:  927GB

Ch2:  927GB

Ch3:  927GB

Ch4:  3721GB

Ch5:  3721GB

Ch6:  Indicates 3721GB but it keeps failing.

I'm thinking of pulling the drive.  Restarting the unit and reinserting it?

[StephenB]

I thought you were replacing the 2 TB drives, not adding to them.

3x2TB + 3x4TB would give you a 14 TB volume size altogether. ("sum the drives and subtract the largest").

3x2TB + 2x4TB would give you a 10 TB volume size (9 TiB)

If you happened to start with a single  2 TB drive installed when you first set up the system, then the 8 TiB growth limit would be reached between 10 and 11 TB. I'm thinking that's what's happened.

If so, reinserting the disk won't help.  You'd need to offload data, do a factory reset, and then restore.  It is possible to do an off-line expansion with ssh, but you should still do a backup first if you want to attempt that.

[peteophoven]

We started the volume with 3 X 1 TB drives.

The volume was around 1800 GB.

We added a 4TB

and then another 4 TB to get us to where we are now - 6400 GB.

Its this last drive that isn't playing nicely.

I fear having to take the drive offline and reformat.  It will be difficult to pull that off.

Highly utilized and maintained production server.  

Thanks for your help.

[StephenB · Accepted solution]

---

@peteophoven wrote:

We started the volume with 3 X 1 TB drives.

---

OK.  That's the same volume size as a single 2 TB drive (except you have redundancy).

Because your starting point was 1.8 TiB, your volume expansion ceiling is 9.8 TiB.

3x1TB + 3x4TB would give you a volume size of 11 TB (or 10 TiB),

The last drive expansion still fails because it would take you over your expansion ceiling (just barely, but still over).

Reformatting the drive won't overcome that.  As I said above, you either need to do off-line expansion with ssh, or do a factory reset and restore the data from backup.

If you do a factory reset, you can switch to OS-6.  Though not supported by Netgear, it doesn't have any known expansion limits.