Need advice on expanding my NAS capacity

TrueNAS General
11

Of course, “redundancy vs. capacity” is the name of the game…
The solution would be to aim for drives larger than the current 8 TB, say 12-16 TB, as a starter for the new pool and progressively replace the 8 TB as you. Initial raw capacity is 4*8 = 24 TB for the mixed 6-wide raidz2 pool, and after replacing the last 8 TB you have one button to press to extend to 4*12 (or whatever). No weird space reporting.

This will be your only way to increase capacity once you have reached the maximum number of drives.

The outline is:

  • optionally unplug the old pool to prevent mistakes while dealing with the CLI
  • Create the degraded pool.
    Attach 4 new drives, format them on the CLI to mimick what TrueNAS would do (this is where some research is needed), create 2 sparse files of appropriate capacity and then create your 6-wide raidz2 with the sparse files and the UUIDs of the real drives
    zpool create newpool raidz2 /home/admin/sparse1 /home/admin/sparse2 UUID1 UUID2 UUID3 UUID4
    (plus probably a few options for compatibility such as -R /mnt)
    then offline the sparse file devices (and delete these files for good measure)
    Once you can export and reimport the degraded pool from GUI, you’re done dealing with the CLI.
  • plug back oldpool (you need to attach 7 drives at this point, but it is acceptable that one lies outside of the semi-open case, with data and power cables coming out…)
  • Replicate your data from oldpool to new pool.
  • Shutdown and detach two drives from oldpool, which you keep as (degraded) offline backup.
  • Take a deep breath and reboot. Degraded newpool should come up; replace one of the missing devices (sparse files) with the remaining old 8 TB drive.
    (At this point, you have two non-redundant copies of your data. Once resilver is complete, newpool has one degree of redundancy.)
  • Power down, bring in another old 8 TB drive, reboot and replace the other missing device with the 8 TB drive (which then destroys oldpool beyond recovery).
  • Rename newpool as oldpool according to the Resource.
  • Wipe the last remaining old 8 TB for use as cold spare.