1. Find degrade hard-disk

root@user-pve:/home/user# /usr/sbin/zpool status -v
  pool: user-storage
 state: DEGRADED
status: One or more devices has experienced an unrecoverable error.  An
        attempt was made to correct the error.  Applications are unaffected.
action: Determine if the device needs to be replaced, and clear the errors
        using 'zpool clear' or replace the device with 'zpool replace'.
   see: http://zfsonlinux.org/msg/ZFS-8000-9P
  scan: scrub repaired 280K in 0 days 04:33:34 with 0 errors on Sun Jan 12 04:57:36 2020
config:

        NAME          STATE     READ WRITE CKSUM
        user-storage  DEGRADED     0     0     0
          raidz1-0    DEGRADED     0     0     0
            sda       ONLINE       0     0     0
            sdb       ONLINE       0     0     0
            sdc       ONLINE       0     0     0
            sdd       ONLINE       0     0     0
            sde       DEGRADED     0     0    74  too many errors

errors: No known data errors
root@user-pve:/home/user#

2. Check hard-disk status

3. Reset degrade status

root@user-pve:/home/user# /usr/sbin/zpool clear user-storage sde
root@user-pve:/home/user# /usr/sbin/zpool status -v
  pool: user-storage
 state: ONLINE
  scan: scrub in progress since Sun Jan 19 19:17:39 2020
        10.7G scanned at 1.53G/s, 1.32M issued at 193K/s, 877G total
        0B repaired, 0.00% done, no estimated completion time
config:

        NAME          STATE     READ WRITE CKSUM
        user-storage  ONLINE       0     0     0
          raidz1-0    ONLINE       0     0     0
            sda       ONLINE       0     0     0
            sdb       ONLINE       0     0     0
            sdc       ONLINE       0     0     0
            sdd       ONLINE       0     0     0
            sde       ONLINE       0     0     0

errors: No known data errors
root@user-pve:/home/user# apt update

4. Verify status in proxmox

After kernel upgrade, ZFS couldn’t start, but some process create some file in the mount point. So after that ZFS can’t start the process ever again. Here’s how to fix.

1. disable service zfs.target and restart.

user@ubuntu:~$ sudo systemctl disable zfs.target

2. after reboot delete or move data in mount point to another location.

3. enable service zfs.target and restart.

user@ubuntu:~$ sudo systemctl enable zfs.target

4. after reboot move data back.