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Hi there,

I鈥檓 not an expert in ZFS (I know enough to be a dangerous fanboy, haha), but I have an unraid server with two ZFS pools: one with HDDs and one with SSDs.

I recently bought a new 4TB Samsung 990 Pro SSD and want to add it to the SSD pool.

My initial thought was to add the 990 to the pool as a new VDEV. However, I鈥檓 also considering recreating the SSD pool with two drives in a strip configuration. I don鈥檛 mind disk failures because I regularly snapshot and back up the SSD pool to the HDD pool.

The main goal is to have access to all 5TB of storage.

I鈥檓 wondering if it鈥檚 a good idea to combine these drives into one pool or if it would be better to create three separate pools.

  • kata1yst@sh.itjust.worksEnglish
    4路
    1 year ago

    Stripes and mirrors have similar read performance. Write performance will suffer in a mirror, though, so it depends on your use case. Personally I鈥檇 go with mirrors, or best of both worlds, mirrors + stripes. Restoring backups and outages are a pain. Of course this halves your storage space, but drives are comparatively cheap. You鈥檙e better off doing something silly like bridging the drives with mergerfs. And no matter what without mirroring or RAID-Z you鈥檙e giving up on ZFS best feature- the check-summing based healing. Better off just yoloing with ext4.

    Hard drives and SSDs should always exist in separate pools, unless you鈥檙e using the SSD as a pool cache for read or write, but realistically outside massive databases or busy virtual machine storage almost no one needs write caching.

    The main reason for separating them is that you鈥檒l get consistent performance from the pool with like hardware, otherwise your performance for reading from the pool will be equivalent to the performance of the slowest drive in the pool.

    • vonProteus@lemmy.mlOPEnglish
      1路
      1 year ago

      Thanks for your perspective.

      I decided to go with the new vdev because:

      • That way, I have access to all 5TB (1TB from the old SSD and 4TB from the new one).
      • One pool is easier to manage than two.
      • I know that I don鈥檛 have auto-healing, and if either of the SSDs fails, I lose the whole pool, and I accept that.

      I did this via:
      zpool add ssdPool /dev/disk/by-id/nvme-Samsung_SSD_990_PRO_4TB-part3

      I don鈥檛 like ext4 because it is not easily backupable (it doesn鈥檛 have snapshots, which are moved periodically to hddPool).