Added new drives to array but forgot to format first. Now it's going in the middle of a 10+ day rebuild!

[MikaelTarquin]

So, I am currently adding 2x 18TB drives to my array, which would be disks 16 and 17. It's been a while but I thought all I had to do was stop the array, add those 2 as additional drives, and start the array to let Unraid do everything. After about a day, things finished by the array showed the 2 new drives as unmountable. I stopped the array again, attempted to remove them, format them xfs like the rest of the array via unassigned devices, and then add them back before starting again.

 

I did several things, so I may be misremembering the exact sequence, but the end result is they now in the array as emulated disks 16 and 17 (I have 2x parity drives, so I wonder what would have happened if I tried 3 at once), and the only option that looked like it would help is Data Rebuild. I kicked that off about 12 hours ago now, and it's 6% complete and averaging anywhere from 5 to 50 MB/s. I assume it's just going to spend the next week or two rebuilding "nothing", at the cost of reading through the entirety of every other drive in the array.

 

Do I really need to just let it go through this Data Rebuild and put all that wear on everything? Or is this likely to fail as well? Is there anything I can do to stop it and add them faster? I assume with those 2 showing emulated, the rest of the array is now unprotected?

nnc-diagnostics-20230807-0956.zip

[JorgeB]

5 minutes ago, MikaelTarquin said:

I stopped the array again, attempted to remove them, format them xfs like the rest of the array via unassigned devices, and then add them back before starting again.

That's not what you needed to do, just needed to press format next to array start, now you need to wait for the rebuild to finish.

[JorgeB]

Forgot to mention, you can format them now, but avoid using them until the rebuild finishes, or performance will suffer.

[itimpi]

For reference the process for adding disks is covered here in the online documentation accessible via the ‘Manual’ link at the bottom of the GUI or the DOCS link at the top of each forum page.

[MikaelTarquin]

So, is it not possible to stop the rebuild and add them without rebuilding again? I guess I don't really understand what the data rebuild could be doing to the new empty drives that's so important. 

[JorgeB]

1 minute ago, MikaelTarquin said:

So, is it not possible to stop the rebuild and add them without rebuilding again?

You can, but would need to do a correcting parity check, and it would take the same time.

[itimpi]

4 minutes ago, MikaelTarquin said:

So, is it not possible to stop the rebuild and add them without rebuilding again? I guess I don't really understand what the data rebuild could be doing to the new empty drives that's so important. 

You said that you formatted them via UD so they were no longer all zeroes.  During the initial add Unraid would have ‘cleared’ them to be all zeroes so parity remained valid.  The rebuild is putting them back to that state.

 

BTW:  you can add as many NEW drives as you want at the same time.   What you cannot do is rebuild more failed drives than you have parity drives.

[JorgeB]

P.S. 10 days for a rebuild seems a lot, probably some controller boatnecks exist.

[MikaelTarquin]

3 hours ago, JorgeB said:

P.S. 10 days for a rebuild seems a lot, probably some controller boatnecks exist.

I'm not sure why it's going so slowly. When I initially added them to the array and it did what I assume was a clear operation, it hummed along at something like 180 MB/sec average (220 at first, and slower as it got to the other side of the disks). I am using the array, which I'm sure doesn't help, but normally parity checks still happen at about 90 MB/sec for me on average (about 3-4 days) Not sure why it's going less than half that now.