Migrating ZFS from using partitions to using the entire disk

I have a simple ZFS setup that I’ve been running for a few years now. When I originally set it up, I created a number of partitions and created a zpool from a partition on each of my two drives, and used the others for booting etc..

Now however I have a separate drive for booting and everything else, so I just want to use the entire drives for my zpool. I recently replaced a drive, so I’m already doing that on one drive:

tank                        ONLINE       0     0     0
  mirror-0                  ONLINE       0     0     0
    ada2                    ONLINE       0     0     0
    ada1p4                  ONLINE       0     0     0

What I want to do now is to replace ada1p4 with ada1, the question is, how do I do that? Is it as simple as zpool replace tank ada1p4 ada1, or is that a bad idea?

1. BACKUP anything you care about… to something off this server.

2. Do the replacement

   zpool set autoexpand=on tank
   zpool offline tank ada1p4
   zpool replace tank ada1p4 ada1
   

3. Wait… and lots of it. Check status with zpool status tank

4. Turn off the autoexpand, zpool set autoexpand=off tank. It’s a best practices thing mostly.

Check more discussion of this question.