Upgrading data and parity drive order

[Homerr]

I have a setup with 17 drives in total including two 8tb parity drives and a 1tb SSD cache.  The data drives are a mix of 1, 2, 3, 4, and 8tb drives.  One of the 4tb drives just failed and I have ordered a 10tb WD Easystore to shuck as a replacement since it was cheaper than any 8tb drive (other than Seagate SMR drives).

 

I know that with this one 10tb drive I won't have more than 8tb usable space and that's fine.  I'm inclined to replace the failed data drive and get back to a non degraded state first.  However, I could pull a parity drive, replace with the 10tb drive, and rebuild the array and then use the 8tb drive as a data drive to replace the failed data pool drive.

 

I'm wondering what happens when:

 

1.  I've added the 10tb drive as a data drive now.  Later I replace the two 8tb parity drives with 10tb (or larger) ones.  Does the ~2tb balance on this data drive then just show up in the array?

 

2.  If I were to replace an 8tb parity drive with the 10tb and then use the old 8tb parity as a data drive - and then add a second 10tb parity drive later.  Presumably after a parity rebuild then 10tb of parity would just be available and I could add other 10tb drives.

 

3.  Is there any difference if in scenario #2 if 8tb parity is replaced with 10tb and 8tb is repurposed as a data pool drive.  Then a 10tb drive is added to the data pool.  Then second parity drive is added replacing the other 8tb parity drive.

 

 

[Hoopster]

28 minutes ago, Homerr said:

I know that with this one 10tb drive I won't have more than 8tb usable space and that's fine.  I'm inclined to replace the failed data drive and get back to a non degraded state first.  However, I could pull a parity drive, replace with the 10tb drive, and rebuild the array and then use the 8tb drive as a data drive to replace the failed data pool drive.

Parity must be as large or larger than the largest data disk.  You can't use the 10TB drive as a data drive with two 8TB parity drives.

 

With dual parity, both do not have to be the same size, so, you can replace parity1 with the 10TB drive and use the old 8TB parity1 to replace the failed data drive.

 

https://wiki.unraid.net/The_parity_swap_procedure

 

37 minutes ago, Homerr said:

 

2.  If I were to replace an 8tb parity drive with the 10tb and then use the old 8tb parity as a data drive - and then add a second 10tb parity drive later.  Presumably after a parity rebuild then 10tb of parity would just be available and I could add other 10tb drives.

^^^This is what you want to do.  As long as one of your parity drives is 8TB, no data drive can be bigger than 8TB.  Once they are both 10TB, then data drives can be 10TB or smaller.

[Homerr]

Hi Hoopster,  my understanding is that a larger drive may be in the array but only the capacity of the parity drive will be recognized.  If this is truly the case, then I am wondering what happens when a larger parity drive is available.

[Hoopster]

46 minutes ago, Homerr said:

Hi Hoopster,  my understanding is that a larger drive may be in the array but only the capacity of the parity drive will be recognized

From the parity swap page I linked:

 

"The replacement drive CANNOT be smaller than the old drive, but it CAN be larger, much larger in fact. If the replacement drive is the same size or larger, UP TO the same size as the parity drive, then there is a simple procedure for that, called Replacing a Data Drive. But if the replacement drive is LARGER than the Parity drive, then a special two-step procedure is required, described on this page. It will use the larger-than-parity drive to first upgrade the parity drive then use the old parity drive to replace the old data drive."

 

That indicates that if a new drive is larger than an existing parity drive, the two-step "replace parity with the larger drive and then old data drive with the old parity" procedure is required.

 

I doubt the wiki is wrong about something so fundamental.  I have personally always followed the above procedure when purchasing a drive larger than the current parity drive(s).

[JorgeB]

1 hour ago, Homerr said:

my understanding is that a larger drive may be in the array but only the capacity of the parity drive will be recognized.

No, not possible.

[Homerr]

Thanks for the replies and setting me straight.

 

I just also bought an 8tb WD Easystore drive from BB, they are on sale again for $130.  I'll swap that in first and then start the 10tb upgrading of the parity drive after everything is stable.