Followed the Clear Drive Then Remove Drive to shrink array but it is still rebuilding parity during parity check. Not sure what I did wrong.

[almon17]

I just had to remove a drive from my array since it started showing SMART errors and I followed the shrink array steps that should not have required a parity rebuild from https://docs.unraid.net/legacy/FAQ/shrink-array/. Prior to shrinking the array I was able to move everything off the drive with the Unbalanced plugin so the drive was empty before starting. Every step completed successfully including the script to clear the array drive. I made sure to remove the drive, check the box that the parity was valid, and then start the array. But during my parity check it is correcting sync errors constantly. Is there something that is commonly missed or a reason why the parity wasn't valid? I was trying to make sure my data was protected during this process but now it's not for the next 2 days. Thanks!

[JonathanM]

4 hours ago, almon17 said:

Every step completed successfully including the script to clear the array drive.

How big was the drive? How many days did the script take to complete?

[almon17]

13 hours ago, JonathanM said:

How big was the drive? How many days did the script take to complete?

The drive is 14 TB. It finished in a couple minutes. I had moved all files off previously so it was empty other than the clear-me directory. The screen said that there was no space left which the script says is expected and if there were no other errors then the drive was cleared so I took that to mean the script executed successfully.

[JonathanM]

4 hours ago, almon17 said:

It finished in a couple minutes.

Then it definitely did NOT write zeroes to the entire capacity of the drive while updating parity to keep it in sync. That would typically take at least as long or longer than a full parity check, probably a day or so under ideal conditions. If the array was still in use while it was writing, I wouldn't be surprised if it took several days.

4 hours ago, almon17 said:

I had moved all files off previously so it was empty other than the clear-me directory.

Empty != clear. Empty means the table of contents has no pointers to files or folders. Deleted files still exist as ones and zeroes across the drive, you can only remove the drive without rebuilding parity if the entire drive has had zeroes written to it.

4 hours ago, almon17 said:

The screen said that there was no space left which the script says is expected and if there were no other errors then the drive was cleared so I took that to mean the script executed successfully.

It definitely did not, based on the length of time it took, as well as...

23 hours ago, almon17 said:

But during my parity check it is correcting sync errors constantly

The time it takes to do a correcting parity check is way longer than the time it takes to do a build from scratch, so if it's less than a quarter completed by now, you should probably stop the check, unassign the parity drive, start the array, stop the array, assign the parity drive, and let it rebuild, followed by a correcting check that should have zero errors.

 

If it's almost done with the correcting check I'd let it finish, then follow it up with another correcting check to make sure you have zero parity errors remaining.

 

That script works for some, fails miserably for others. This is the second time in the last week or so I've seen the same thing reported. There is a reason it's only in the legacy documentation and hasn't been moved to the current docs. When first authored it worked well, but something in newer configs seems to be causing issues.

 

23 hours ago, almon17 said:

I was trying to make sure my data was protected during this process but now it's not for the next 2 days.

Keep in mind that valid parity can recover a failed drive as long as all the rest of the data drives are able to be read perfectly, but it doesn't protect your data from user error or corruption. You must still keep a second copy of data that you feel is irreplaceable somewhere other than the server. You probably don't have to back up the entire content of your server, but if it can't be replaced from another source, either your backups or the internet in general, it's not protected. Unraid or any RAID only covers a subset of things that can eat your data.