Encrypted ZFS datasets empty after manual mount

[Athlon]

Hello!
I am struggling with a quite weird problem imho.
Running Proxmox 7.4.1 (without subscription) without any issues for a long time until recently the SATA controller card locked up and I had to do a hard shutdown. Connected the 4 harddrives to the internal ports and booted up.
The pool "ZFS_2" is encrypted and gets mounted using zfs mount -l ZFS_2 after logging in via SSH:

zfs get mounted
NAME                          PROPERTY  VALUE    SOURCE
ZFS_2                         mounted   yes      -
ZFS_2/Backups                 mounted   yes      -
ZFS_2/Multimedia              mounted   yes      -

However, df -h shows an incorrect size for the dataset "Backups" and Multimedia and the mountpoints /mnt/ZFS_2/Backups & /mnt/ZFS_2/Multimedia appear to be empty:

Filesystem                    Size  Used Avail Use% Mounted on
...
ZFS_2                          46T   23T   24T  50% /mnt/ZFS_2
ZFS_2/Backups                  24T  256K   24T   1% /mnt/ZFS_2/Backups
ZFS_2/Multimedia               24T  256K   24T   1% /mnt/ZFS_2/Multimedia

The zfs get canmount command is set:

NAME                          PROPERTY  VALUE     SOURCE
ZFS_2                         canmount  on        default
ZFS_2/Backups                 canmount  on        default
ZFS_2/Multimedia              canmount  on        default

As it turns out, for a brief moment, after manually unmounting using zfs unmount ZFS_2/Backups and immediately listing the mountpoint's content using ls /mnt/ZFS_2/Backups/ the directory structure including files and subdirectories is visible. After two seconds the command ls /mnt/ZFS_2/Backups/ returns an empty mountpoint again - apparently the zfs mount command has performed another mount. This is also true for the Multimedia directory. I read up a lot about "double mounting", "empty mount directories" etc. but did not find a permanent solution yet unless i set the canmount=off for the pool "ZFS_2" and its datasets.
I suspect some misconfiguration in my proxmox setup (Cache?) or on the pool "ZFS_2" since my other pool "ZFS" never showed this behaviour. Any help would be greatly appreciated!

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Additional information:
SMART tests using smartctl -t long for all four drives finished without error.
The command zpool status shows no errors:

pool: ZFS_2
 state: ONLINE
  scan: scrub repaired 0B in 21:13:41 with 0 errors on Mon Dec 23 16:51:42 2024
config:

        NAME                                   STATE     READ WRITE CKSUM
        ZFS_2                                  ONLINE       0     0     0
          raidz1-0                             ONLINE       0     0     0
            ata-ST18000NM000J-2TV103           ONLINE       0     0     0
            ata-ST18000NM000J-2TV103           ONLINE       0     0     0
            ata-ST18000NM000J-2TV103           ONLINE       0     0     0
            ata-ST18000NM000J-2TV103           ONLINE       0     0     0

errors: No known data errors

zpool --version
zfs-2.1.15-pve1
zfs-kmod-2.1.15-pve1

 

[waltar]

That's the zfs pod lid special feature to even not show data if still encrypted yet. Use canmount off with systemd unit for mount after key is given.