So, let’s say you’ve just completed migrating to ZFS from UFS using LiveUpgrade, and now you want use that leftover disk to make a mirror. Easily done, but there’s one caveat – you need to make the second disk bootable in case the first fails. So, starting off from where we left off, you have an old UFS based boot environment sitting on c1t1d0. First, delete the old environment:

ludelete Solaris10 && lustatus

That was easy. Now run ‘format’ on c1t1d0, and make slice 0 encompass the whole disk. Write out the label, and get back to the prompt. Now, we need to make our single-disk ZPool into a two-way mirror. This operation is mind- blowingly simple and is one of the showcases of ZFS and its ease of management:

zpool attach rpool c1t0d0s0 c1t1d0s0

This sets up the mirror, and automatically starts the resilvering (syncing) process. You can monitor its progress by running ‘zpool status’. The final step is to actually make c1t1d0 bootable in case c1t0d0 fails. Here, we use the ‘installboot’ program for SPARC:

installboot -F zfs /usr/platform/`uname -i`/lib/fs/zfs/bootblk /dev/rdsk/c1t1d0s0

or use installgrub if you’re on x86:

installgrub /boot/grub/stage1 /boot/grub/stage2 /dev/rdsk/c1d0s0

That’s it, you can now boot from either drive!