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Unfortunately I do not really understand zfs. I have a Proxmox 5 node with 5 300GB disk in raidz2. History: 

zpool create -f -o cachefile=none -o ashift=12 rpool raidz2 /dev/sda2 /dev/sdb2 /dev/sdc2 /dev/sdd2 /dev/sde2

I would like to remove a disk from zpool to use it for others, but not zfs, but ext4.

My question is that disk deletion is possible? If yes, how?

Thank you, Laszlo

Laszlo Malina
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1 Answers1

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No, not directly. Z1/Z2/Z3 vdevs cannot be broken up or increased with additional disks, so your first decision is permanent.

You have one of these alternatives to achieve your goal:

  • zfs send | zfs recv your pool data to another pool, zpool destroy your old pool, zpool create your new pool with fewer disks, zfs send | zfs recv your data back.
  • As user449299 suggested in the comments: Create a zvol inside your pool, format it as ext4 and mount it as a normal filesystem.
  • Remove the disk from the system, your pool will now be in degraded state (essentially being a Z1 instead of Z2 temporarily). Format the disk, add it to the system again and use it as an independent disk.
user121391
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  • Thank you, I read something like this. I wanted to measure whether the zfs itself was bad for the performance of the IO system? Finally I put a separate disk, which I did not put under zfs. I can not tell if it was better because application problem was in a VPS, it was slow, not the host. Although it is very confused that zfs uses a lot of memory. I tried to measure it with ioping, but it gave me a very strange result, 1Gb, which is not realistic :) 671.1 k requests completed in 3.00 s, 274.2 k iops, 1.05 GiB/s Otherwise, I have no other problem. – Laszlo Malina Jan 18 '18 at 14:35
  • @LaszloMalina For benchmarking either user iostat or (better) benchmark with your actual applications. Synthetic benchmarks are only estimates. Yes, ZFS uses more memory than other systems, mostly because of the ARC (adaptive replacement cache). If you are very memory-constrained (smaller than 2 GB) and want speed more than safety, it may not be your best choice. – user121391 Jan 19 '18 at 08:06