Prevent disk reordering on boot

Question

I have 3 physical drives in my Mac Pro with OSX 10.6.4. Occasionally after rebooting the machine, the disk numbering changes such that the /dev/disk# does not reference the same drive as it did before the reboot.

Example

/dev/disk0 -> 64GB SSD drive
/dev/disk1 -> 640GB Hitachi
/dev/disk2 -> 160GB WD (BootCamp)

After rebooting the mapping might be

/dev/disk0 -> 160GB WD (BootCamp)
/dev/disk1 -> 640GB Hitachi
/dev/disk2 -> 64GB SSD drive

Even more confusing is that the remapping is not consistent. For most stuff this is irrelevant. However I also have Parallels installed to allow access to the BootCamp partition from within OSX. Parallels uses the /dev/disk# path in it's configuration file so, after rebooting OSX I launch Parallels and it tells me that the disk is no longer present.

Is there a way to tell OSX to always assign a given drive to /dev/disk0?

Answer 1

There does not seem to be a way to specify a device for a given drive. Your best bet might be to not auto-mount, then use a LaunchAgent to mount them in the order you want with a pause between each mount, and see if it works that way. This method might get messed up if you have a USB key or something else that auto-mounts available to the system when you boot.

Answer 2

One trick I've used to solve your Parallels use case is to have the config file point to a symbolic link file, and then update the symlink to point to the correct device before starting the vm.

If you're comfortable writing scripts, you could use a shell script like this to determine the device name and update the symlink based on the volume name:

 BOOTCAMP_DEVICE=`mount | grep BOOTCAMP | cut -f 1 -d ' '`
 ln -f -s $BOOTCAMP_DEVICE path_to_symlink