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  • ZFS - Pool Fails to Import on Array Start

    • Urgent

    Zpool that includes log, cache, and special devices (partitions on a group of 3 NVME drives) will not import on array start.  Pool can be imported from the CLI, requiring services to be restarted to work properly.  Pool topology is shown below.  Special, cache, and log VDEVs are comprised of partitions on a group of 3 NVME drives.

      pool: mainpool
     state: ONLINE
      scan: scrub repaired 0B in 00:22:50 with 0 errors on Sun Apr 23 23:38:41 2023
            NAME           STATE     READ WRITE CKSUM
            mainpool       ONLINE       0     0     0
              mirror-0     ONLINE       0     0     0
                sde1       ONLINE       0     0     0
                sdf1       ONLINE       0     0     0
              mirror-1     ONLINE       0     0     0
                sdg1       ONLINE       0     0     0
                sdh1       ONLINE       0     0     0
              mirror-3     ONLINE       0     0     0
                nvme4n1p2  ONLINE       0     0     0
                nvme5n1p2  ONLINE       0     0     0
                nvme6n1p2  ONLINE       0     0     0
              mirror-2     ONLINE       0     0     0
                nvme4n1p1  ONLINE       0     0     0
                nvme5n1p1  ONLINE       0     0     0
                nvme6n1p1  ONLINE       0     0     0
              nvme4n1p3    ONLINE       0     0     0
              nvme5n1p3    ONLINE       0     0     0
              nvme6n1p3    ONLINE       0     0     0
    errors: No known data errors



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    Recommended Comments


    Special, cache, and log VDEVs are comprised of partitions on a group of 3 NVME drives.


    This is not supported, at least not for now, each device can only be used once for a pool, and zfs must be on partition #1.

    Link to comment

    In the release notes, it mentions reporting zpools topologies that won't import, so I wanted to file the report so it can be added to the list of ZFS topology possibilities to be considered going forward.  The idea of splitting up a very high performance NVME into partitions and using those partitions to serve multiple functions is quite common when balancing availability and performance in ZFS special, cache, and log VDEVs.

    Edited by Keliaxx
    Link to comment

    It would be a good option, but because Unraid uses one device per slot, and that device will have a single function for the pool, it might not be easy to implement, but lets see what LT thinks.

    Link to comment

    As a bit of an addendum around NVME and ZFS, but also applicable to NVME in general is that underprovisioning NVME is extremely common for extending its service life.  A lot of modern controllers no longer provide the option to underprovision or create separate domains at the hardware level, so it is now accomplished through partitioning.  Fully supporting NVME use cases really does require having the ability to work with partitions as well as entire devices IMHO.

    Link to comment

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