I have a healthy array made up of 2TB disks and I now want to add a 3TB disk. I don't care whether I add 2T or 3T to the array right now (3TB is now cheaper per TB than 2TB disks in the UK) so I thought I could just add it as a data drive. Unraid won't let me do this as the parity drive is smaller, it tells me

 

Disk in parity slot is not biggest.

 

and

 

If this is a new array, move the largest disk into the parity slot. If you are adding a new disk or replacing a disabled disk, try Parity-Swap.

 

Sadly I can't find anything that tells me what the "Parity-Swap" procedure is though.

 

If I set the new 3TB disk as parity and leave the old parity unassigned then it says I will be upgrading parity. I have performed a parity check since writing anything to the array and the new disk has been precleared 3 times.

 

Is this the right/safe approach to take here?

 

Thanks

Matt

PUt all the data disks back to where they were. (all the 2 TB disks.)

They should all still have your data on them.

The Parity Drive currently in place (also a 2 TB disk) should be valid.

Run a correcting parity check to be sure.

 

Then remove the existing parity drive.

Insert the 3 TB disk and assign it as Parity.

Parity will rebuild on the new 3TB drive.

AT that point, you'll NOT have added 'capacity' to your unRAID, BUT you can then begin to swap in larger data drives.

 

 

Just for further information parity-swap is a special case where you need to replace a failed data disk and the replacement disk is larger than your parity drive.  You cannot simply upgrade the parity drive and recalculate parity as you have data that needs recovering.  This process has to carry out additional work:

• Copy the old parity contents to the new parity drive (and clear any additional space as it is larger than the old drive)
  
• Use the new parity drive to rebuild the data that was on the failed data disk onto the disk that was the previous parity drive (as it is now the replacement for the failed data disk).

In your case you appear to have a valid system and are not trying to recover a failed disk.  In such a case it is easier (and safer) to follow the procedure outlined above and simply replace the parity drive with the new disk and rebuild parity from the data drives.

PUt all the data disks back to where they were. (all the 2 TB disks.)

They should all still have your data on them.

The Parity Drive currently in place (also a 2 TB disk) should be valid.

Run a correcting parity check to be sure.

 

Then remove the existing parity drive.

Insert the 3 TB disk and assign it as Parity.

Parity will rebuild on the new 3TB drive.

Then do another parity check (I would do a non-correcting check, since you know it should be correct).  Until that further check is done you cannot be certain that the new parity can be read correctly.  After that, the old parity drive can be reused.  I would do a single pre-clear pass on that drive, partly to check the drive but also to clear it before you add it back to the array as a new data drive.

Refer to my "how to" post on upgrading parity in my sig.

Thanks for all the replies. I worked through this without a hiccup (albeit it didn't take me the best part of 2 months to run, I just hadn't got round to it til recently!).