I recently bought a QNap NAS and decided to try out a few NAS OS, amongst which TrueNAS. After creating a ZFS pool on TrueNAS and transfering a few files, I got disatisfied with TrueNAS and decided to try out QNap’s OS (QuTS). Both OS are installed on the NAS. I went through QuTS initialization, noticed that QuTS didn’t automatically import the ZFS pool and got disatisfied with QuTS’ interface. After what I decided to reinstall TrueNAS along with QuTS (QuTS had erased the disk on which TrueNAS was installed, which is different from the disks in the ZFS pool). And this is the current state of affairs.

The ZFS pool in question contains 3 disks of capacity 5To each. TrueNAS shows the pool in its interface, but is not able to mount it. The pool is named main-pool. Following are different commands that I tried and their results:

# zpool import -a
no pools available to import

# zpool status -v
  pool: boot-pool
 state: ONLINE
  scan: scrub repaired 0B in 00:00:08 with 0 errors on Sun Sep 22 03:45:10 2024
config:

        NAME         STATE     READ WRITE CKSUM
        boot-pool    ONLINE       0     0     0
          nvme0n1p3  ONLINE       0     0     0

errors: No known data errors

# zpool status -v main-pool
cannot open 'main-pool': no such pool

# zdb -l /dev/sd{b,c,e}    
failed to unpack label 0
failed to unpack label 1
------------------------------------
LABEL 2 (Bad label cksum)
------------------------------------
    version: 5000
    name: 'main-pool'
    state: 0
    txg: 4
    pool_guid: 8298165464761202083
    errata: 0
    hostid: 1555077055
    hostname: 'nas'
    top_guid: 4887568585043273647
    guid: 12714426885291094564
    vdev_children: 1
    vdev_tree:
        type: 'raidz'
        id: 0
        guid: 4887568585043273647
        nparity: 1
        metaslab_array: 128
        metaslab_shift: 34
        ashift: 12
        asize: 15002922123264
        is_log: 0
        create_txg: 4
        children[0]:
            type: 'disk'
            id: 0
            guid: 12714426885291094564
            path: '/dev/disk/by-partuuid/8b808c7a-cacd-46d1-b400-9f8c71d51b30'
            whole_disk: 0
            create_txg: 4
        children[1]:
            type: 'disk'
            id: 1
            guid: 822100609061977128
            path: '/dev/disk/by-partuuid/8965dbb6-9484-4da5-ba1b-d33303b19ae5'
            whole_disk: 0
            create_txg: 4
        children[2]:
            type: 'disk'
            id: 2
            guid: 1731788408784132969
            path: '/dev/disk/by-partuuid/fae9eb3e-e782-4115-bbc9-cde4dc72c408'
            whole_disk: 0
            create_txg: 4
    features_for_read:
        com.delphix:hole_birth
        com.delphix:embedded_data
        com.klarasystems:vdev_zaps_v2
    labels = 2 3 

Weirdly, it seems like I can import each disk separatly, by dev path:

# zpool import -d /dev/sdb                               
   pool: main-pool
     id: 8298165464761202083
  state: UNAVAIL
status: The pool was last accessed by another system.
 action: The pool cannot be imported due to damaged devices or data.
   see: https://openzfs.github.io/openzfs-docs/msg/ZFS-8000-EY
 config:

        main-pool                                 UNAVAIL  insufficient replicas
          raidz1-0                                UNAVAIL  insufficient replicas
            sdb                                   ONLINE
            8965dbb6-9484-4da5-ba1b-d33303b19ae5  UNAVAIL
            fae9eb3e-e782-4115-bbc9-cde4dc72c408  UNAVAIL

But not all of them together:

# zpool import -d /dev/sdb -d /dev/sdc -d /dev/sde                   
   pool: main-pool
     id: 8298165464761202083
  state: UNAVAIL
status: The pool was last accessed by another system.
 action: The pool cannot be imported due to damaged devices or data.
   see: https://openzfs.github.io/openzfs-docs/msg/ZFS-8000-EY
 config:

        main-pool   UNAVAIL  insufficient replicas
          raidz1-0  UNAVAIL  insufficient replicas
            sdb     UNAVAIL  invalid label
            sdc     UNAVAIL  invalid label
            sde     UNAVAIL  invalid label

So… Is my ZFS pool lost?

If so, then how do people recover a ZFS pool when the system has crashed before the ZFS pool was correctly exported? For instance if the disk containing the system fails?