Let me start by saying, I am new to Unraid.  I am migrating from a Synology Diskstation.

 

I had initially built an array with 4x 14TB drives, 1x parity and 3x data.  I am adding some 16TB drives so I need to upgrade my parity disk.  I precleared 6 of my 8x 16TB drives.  I didn't preclear 2 of them because they came later.  I added them in, planning to preclear them after adding the others that were already done.  I removed the 14TB parity disk and replaced it with a 16TB drive.  I also added a 2nd 16TB parity.  My array is currently rebuilding.  I noticed that there are 6x 16TB drives in the unassigned devices pane however 5x of them have been precleared and only 1 of them has not been.  This means that I accidentally made 1 of the non-precleared drives a parity disk.

 

Does the rebuild automatically clear the drive?  If not, is there something I can do to fix this?

 

Thanks for your help!

Preclear is only for testing disks. There is only one scenario where Unraid needs a clear disk, when ADDING a disk to a NEW data slot in an array that already has valid parity. This is so parity will remain valid, since a clear disk is all zeros and so has no effect on parity. In that one and only scenario, if you don't preclear the disk, Unraid will clear it anyway.

 

So, preclear is only for testing disks. Building parity or rebuilding a data disk does not clear a disk since it doesn't need to be clear. If you have already built parity then I would just forget about testing it since building (or rebuilding) already writes every bit of the disk. Just do a parity check and be sure to setup Notifications to alert you immediately by email or other agent as soon as a problem is detected.

Thanks for your reply!

 

OK, so adding any drive to a new data slot requires a cleared disk.  And if I don't preclear prior to adding the disk, Unraid will clear for me but the array will be down while doing so, correct?  And any time a disk is replaced/swapped/etc, and a rebuild occurs, the disk does not need to be precleared?  ...But it's probably a good idea because the act of preclearing will test the disk as well?

 

Do I have that correct?

1 minute ago, GPT347 said:

Unraid will clear for me but the array will be down while doing so, correct? 

No the array won't be down that was only for old versions of Unraid. But the new disk won't be available until it is cleared and formatted.

 

Some people test with preclear, you can also test with the disk manufacturers utility. Sometimes I don't bother to test, but I put a new drive in my server rarely and never more than one at a time. And I have good (enough) backups.

Awesome.  Thanks again.