In general, older pool versions can be read by newer systems, but not the other way round (that is, after you do a
zpool upgrade on your pool, you cannot go back without destroying the whole pool).
Therefore, I would first try the simple approach:
- Do a full backup and test if you can go back to that backup without problems.
- Remove any log or cache devices from the pool if you have them attached.
- Stop all input/output on the pool, for example network sharing services.
zpool export the pool.
- Shutdown the system, swap one or two discs over to the new one.*
- Install your base system on another disk.
zpool import the pool.
- Optionally, add the second disk if you only added one and wait for the resilver to complete.
*) In theory, you would always swap both disks because you have a working backup anyways. I just like the peace of mind to always have another working disk in the old system, should I mess anything up. Much faster to go back this way than with backups, and the chance that a bitflip occurs in the 5 minutes between swapping is minimal.