LinuxQuestions.org - ZFS remove/replace root vdev

Hello all,

I have been reading up on ZFS, and I'm about ready to take the plunge. I see that adding new root vdevs (zpool add mypool raidz /dev/c0t0d0 /dev/c0t1d0 /dev/c0t2d0) is a snap. However, I don't see anything in the docs about removing a root vdev. Here's a hypothetical situation:

A zpool is made of three vdevs, made of three raidzs. The first has 1 Tb of space. Each of the two other raidzs has 100 Gb of space (for a total of 1.2 Tb). The pool itself is barely used, and only has 100 Gb worth of files stored, with no snapshots or clones. Say I want to remove the third raidz. Can I do this without having to back up elsewhere, recreate the pool, and transfer everything back over? Even without the third root vdev, there is still plenty of space for all the files (1.1 Tb is plenty for 100 Gb). However, there doesn't seem to be a way to do this cleanly.

A more graphical representation:

Code:

mypool (1.2 Tb total - 100 Gb used)

  raidz (1 Tb total)

      disk1 (500 Gb)

      disk2 (500 Gb)

      disk3 (500 Gb)

  raidz (100 Gb total)

      disk4 (50 Gb)

      disk5 (50 Gb)

      disk6 (50 Gb)

  raidz (100 Gb total)

    disk7 (50 Gb)

    disk8 (50 Gb)

    disk9 (50 Gb)

... and I want to go to...

Code:

mypool (1.1 Tb total - 100 Gb used)

  raidz (1 Tb total)

    disk1 (500 Gb)

    disk2 (500 Gb)

    disk3 (500 Gb)

  raidz (100 Gb total)

    disk4 (50 Gb)

    disk5 (50 Gb)

    disk6 (50 Gb)

The ultimate reason is for the future. If I can't get a replacement disk for a root vdev(because the disk itself is just to outdated...I have 9 18Gb SCSI disks here), then I will need to remove a root vdev in the future.

Thanks.