itimpi

No. A parity sync overwrites everything on a drive so existing contents are irrelevant. As a point to note a preclear is never NEEDED. It is just often done as a confidence check on a drive. You might find this section of the online documentation that discusses this to be of interest.

CMR is fine - it is SMR that can be very slow once the drives internal buffer gets full.

Yes - it is going to take forever. I normally expect it to take ~2 hours per TB as a rule of thumb so MUCH quicker than you are currently getting. Before doing anything you might want to have a quick look at the syslog (via button at top right of GUI to see the continual reset on ata2 (which is the parity2 drive) as that shows you the symptom in the log when you have such an issue.

Can you swap the disk to another position? Unraid does not care where drives are connected as it identifies them by serial number.

What about the power to the drive? The noises could be an indication of insufficient power. Do you use power splitters to get enough connections - they can cause problems. You could try swapping the power cables with another drive to see if the problem stays with the drive or moves with the cable change.

You are getting continual resets on parity2. You should carefully check the power and SATA cabling to the drive.

Yes. Do you have anything accessing the array? This will severely affect the parity sinc speed whole it is happening.

The writing to disk6 is likely the culprit as the writes to that drive corresponds to the number of writes to the parity drives, The reading from other drives is probably just a consequence of the parity check running.

The PHP code I use in my Parity Check Tuning plugin is: exec ("ps -ef | grep mover", $output); $ret = (count($output)> 2) ? 1 : 0; You should be able to adapt this to the script you want to run?

Unless you have a very old CPU then doing 2 parity drives at the same time can run at a similar speed to doing a single one. If the new parity drive is slower, that WILL slow things down as the speed is determined by the slowest drive at any point in the check. I wonder if the new WD parity drive is using SMR technology rather than CMR as that could make a big difference .

According to your diagnostics you have 2 disks with problems and only single parity. Disk9 is missing and disk5 is disabled.

Can you successfully stop the array? What is the name of the folder that will not delete? Probably not relevant but just might give a clue. Have you run a check filesystem on the cache pool?

You might also want to check your motherboard manual in case adding the m2 ssd disables something else.

Have you removed the 2 files it is telling you are corrupt? They should be human readable text but if you look at them I suspect they are not.

Just keep an eye on this. If it stays stable you should be fine, but if it starts steadily increasing then it is probably time to consider replacing the drive.