I currently have a pool with 2 vdevs. one with 5 18TB drives, and one with 5 20TB drives. Both vdevs use raidz-1. The data is not critical so data loss would not be catastrophic. That said this is a bad setup.
I would like to move this to 10 28TB disks in 1 vdev with raidz-2.
As I understand it there is no direct path to merge vdevs or even to change the raid-z setup in a given vdev. Am I correct?
What should be the approach here? I do not have 10 spare slots to create a whole new pool. I don’t have the space for a full backup elsewhere (again, not critical data).
Correct. Neither TrueNAS nor ZFS support direct migration in this situation.
This is no approach that does not include full backup and restore.
That said, if your data fits on fewer 28TB disks in a RAID-Z2, and you have slots for them, you could migrate the data from the current pool to a new pool. Then, with that done, you can remove the old pool disks, and expand your new pool’s RAID-Z2 vDev. It’s not perfect, but it’s the only chance you have. (As far as I know…)
ZFS is not the most flexible file system, volume manager and RAID scheme available. At present, ZFS does not allow RAID-Zx vDev removal. Nor RAID-Z1 to RAID-Z2 in place migration.
