TS-231P RAID 1: rebuild after disk replacement aborted by "unrecovered read error" on the source disk – options?

English Storage
1

Model: QNAP TS-231P, QTS 5.2.10.3577, 1 GB RAM.
Setup: 2 x 2 TB in RAID 1 (thick volume, ~1 TB of data), replacing both with 2 x 4 TB (WD40EFZZ).

What happened:

  1. First attempt (replace disks one by one) failed. Later diagnostics showed the system partitions (md9/md13) had only one member (HDD 1), and the other disk had a read error.
  2. Second attempt: I replaced HDD 2 with a new 4 TB. The rebuild started, but after ~11 minutes the log showed on HDD 1 (the only remaining disk): “Read I/O error, UNRECOVERED READ ERROR / Medium error”, then “Skipped rebuilding RAID group 1”.

Current state:

  • Pool and volume “Degraded”, running only on the old HDD 1 (SMART warning).
  • The new 4 TB shows “Good” and appears in the RAID group, but “Rebuild RAID group” shows “Available disks: 0/2”, so I can’t start the rebuild again.
  • BBM shows “No” and I can’t find any option to enable it.
  • Data is backed up to Dropbox via HBS (real-time sync), and the old HDD 2 is kept untouched.

Questions:

  1. Is there a safe way to resume the resync or to make QTS skip/mark the unreadable sector instead of aborting?
  2. How can I make the new 4 TB appear as a free disk again so I can retry the rebuild, without losing the array?
  3. If not, is my plan reasonable? Copy all data to an external USB drive (file-level, which should only fail on affected files), then install both 4 TB disks fresh, create a new RAID 1, restore the config .bin, and restore the data.

Has anyone seen this with a failing source disk? Thanks!

2

As you have backups, clear both new disks and start the NAS fresh.

Then restore the datavfrom backups

3

You could remove and reinsert it, while the NAS is powered on. Which makes me wonder if you initially tried to replace the drives while the NAS was powered on or off ?

That said, if the HDD 1 is labelled failed, it wouldn’t work.

Maybe you could power off the NAS, reinsert the original HDD 2, and power on. Then see the array status. And run bad block scans on the drives. If both drives are ok, try the replace one by one again.

If both HDD 1 and 2 are failed, you would have to create a new RAID with the new drives