Can ZFS storage pools share a physical drive w/ the root (UFS) file system?

Question

I wonder if I'm missing something here, because I was under the impression ZFS offered ultimate flexability until I encountered the following fine print 50 pages into the ZFS Administration Guide:
"Before creating a storage pool, you must determine which devices will store your data. These devices must be disks of at least 128 Mbytes in size, and _they must not be in use by other parts of the operating system_. The devices can be individual slices on a preformatted disk, or they can be entire disks that ZFS formats as a single large slice."
I thought it was frustrating that ZFS couldn't be used as a boot disk, but the fact that I can't even use the rest of the space on the boot drive for ZFS is aggrivating. Or am I missing something? The following text appears elsewhere in the guide, and suggests that I can use the 7th slice:
"A storage device can be a whole disk (c0t0d0) or _an individual slice_ (c0t0d0s7). The recommended mode of operation is to use an entire disk, in which case the disk does not need to be specially formatted."
Currently, I've just installed Solaris 10 (6/11) on an Ultra 10. I removed the slice for /export/users (c0t0d0s7) from the default layout during the installation. So there's approx 6 GB in UFS space, and 1/2 GB in swap space. I want to make the 70GB of unused HDD space a ZFS pool.
Suggestions? I read somewhere that the other slices must be unmounted before creating a pool. How do I unmount the root partition, then use the ZFS tools that reside in that unmounted space to create a pool?
Edited by: MindFuq on Oct 20, 2007 8:12 PM

Answer 1

It's not convenient for me to post that right now, because my ultra 10 is offline (for some reason the DNS never got set up properly, and creating an /etc/resolv.conf file isn't enough to get it going).
Anyway, you're correct, I can see that there is overlap with the cylinders.
During installation, I removed slice 7 from the table. However, under the covers the installer created a 'backup' partition (slice 2), which used the rest of the space (~74.5GB), so the installer didn't leave the space unused as I had expected. Strangely, the backup partition overlapped; it started at zero as the swap partition did, and it ended ~3000 cylinders beyond the root partition. I trusted the installer to be correct about things, and simply figured it was acceptible for multiple partitions to share a cylinder. So I deleted slice 2, and created slice 7 using the same boundaries as slice 2.
So next I'll have to remove the zfs pool, and shrink slice 7 so it goes from cylinder 258 to ~35425.
[UPDATE] It worked. Thanks Alex! When I ran zpool create tank c0t0d0s7, there was no error.
Edited by: MindFuq on Oct 22, 2007 8:15 PM