Macintosh HD won't unmount

[JoBoy]

I'm asking this question here because Sandbox and Macintosh HD volumes share data.

In attempting to do routine maintenance, I booted from a current, bootable clone on an external Firewire drive. Using the clone's Disk Utility app, I performed Repair Disk and Repair Disk Permissions on the Sandbox volume. I then attempted to perform the same operations on Macintosh HD, but that volume would not unmount. I tried to do the same thing while booted from another clone and obtained the same results. I then booted from the Snow Leopard install disk and was able to perform both operations on both volumes without incident. I then booted from the external Firewire clone and attempted to use the installed Disk Warrior app. Rebuilding the directory on Sandbox went just fine, but Macintosh HD would not unmount. I then booted from the Disk Warrior 4.1 install disk and was able to rebuild the directories on both disks without incident. There is one other fact that may be useful. The installed version of Disk Warrior is 4.2. Since making that installation, the DW 4.2 DVD was scratched and cannot boot, so I was forced to go back to the 4.1 install disk to do the operations from an install disk. I'm using Snow Leopard 10.6.2 as my regular OS, but the boot OS on the DW 4.1 install disk is 10.5.6. Is there an SD! issue that would explain these results?

[dnanian]

A Sandbox explicitly references and uses the files that are shared from the original drive.

[JoBoy]

I know that. It's in the User Guide, but does it have anything to do with why Macintosh HD won't unmount? BTW, sorry for accidentally putting this question in the wrong forum. I'd move it if I knew how.

[dnanian]

Yes. Items are shared from it, so the drive is busy.

[JoBoy]

How can the drive be busy when the machine is booted from an external clone and the drive I'm trying to do maintenance on is the main internal drive?

[dnanian]

You said you're using a Sandbox, right?