Of course, this only shrinks the whole volume, but it is my understanding that at that point, you can re-arange the plexes so that the disk you want to remove no longer has any plexes on it. It's ugly and complex, but possible. It strikes me as very strange that a system that's otherwise so flexible does not allow this. We've really hosed ourselves because on one Filer (while attempting to set up a volume that we could volcopy to), we accidentally added disks to the root volume. So, now we have to do what? Re-install?
-- Aaron Sherman
I had to do something similar in a case where we wanted to remove some data disks from the root volume.
You create a new volume and then copy the contents of the root volume to the new volume.
Then you use the vol options root command to make the new volume the root.
Reboot the filer. This makes the new root volume take over.
Rename the old root volume to a temp name.
Rename the new root volume to be the old root volume name.
Offline the old root volume.
Reboot the filer. This allows you to destroy the old root volume.
Use vol destroy to get rid of the old root volume.