Switched On Tech Design

Tag: pool

  • ZFS: Adding a new mirror to an existing ZFS pool

     

    Mirrored vdevs are great for performance and it is quite straight-forward to add a mirrored vdev to an existing pool (presumably one with one or more similar vdevs already):

     

    zpool add [poolname] mirror [device01] [device02] [device03]

     

    If it’s a two-way mirror you will only have two devices in the above. An example for ZFS on Ubuntu with a pool named seleucus and two SSDs could look like:

     

    zpool add seleucus mirror ata-SAMSUNG_SSD_830_Series_S0XYNEAC705640 ata-M4-CT128M4SSD2_000000001221090B7BF9

     

    As always, it’s good practice to use the device name found in /dev/disk/by-id/ rather than the sda, sdb, sdc etc. names as the latter can change – the former do not.

  • How do you tell which zpool version you are running?

    This is a question that crops up fairly regularly, as different operating systems support different zpool versions. Fortunately, it’s quite easy to find out which versions you are running – simply run:

     

    # zpool upgrade

     

    If you want a more detailed readout, including the features of the pool version you have, try:

     

    # zpool upgrade -v

     

    Your output should look something like this:

     

    # zpool upgrade -v
    This system is currently running ZFS pool version 28.

    The following versions are supported:

    VER  DESCRIPTION
    —  ——————————————————–
    1   Initial ZFS version
    2   Ditto blocks (replicated metadata)
    3   Hot spares and double parity RAID-Z
    4   zpool history
    5   Compression using the gzip algorithm
    6   bootfs pool property
    7   Separate intent log devices
    8   Delegated administration
    9   refquota and refreservation properties
    10  Cache devices
    11  Improved scrub performance
    12  Snapshot properties
    13  snapused property
    14  passthrough-x aclinherit
    15  user/group space accounting
    16  stmf property support
    17  Triple-parity RAID-Z
    18  Snapshot user holds
    19  Log device removal
    20  Compression using zle (zero-length encoding)
    21  Deduplication
    22  Received properties
    23  Slim ZIL
    24  System attributes
    25  Improved scrub stats
    26  Improved snapshot deletion performance
    27  Improved snapshot creation performance
    28  Multiple vdev replacements

    For more information on a particular version, including supported releases,
    see the ZFS Administration Guide.

     

    Or for the more simple command:
    # zpool upgrade

     

    This system is currently running ZFS pool version 28.

    All pools are formatted using this version.