VM : High Number of VHD’s – Boot Order Issues
Encountered an issue with a VM that had around 15 VHDs and multiple SCSI buses. After testing this a few times I discovered that on adding the 8th drive the boot order changed to: 1:0, 1:1, 1:2… 1:7 – this was automatic, I never changed the boot order.
To make matters worse, you can only see 8 VHDs in the VM BIOS, so it is impossible to change the primary boot disk to 0:0 again!
Workaround – I figured, lets move the boot volume to SCSI channel 1 and the data disks to an other controller. I move the data disks to channel 2/3 and the system booted. So, my system disk was on 1:0, additional disks were on channels 2:X and 3:X.
Update 02/02/2012: You can also set the boot drive in the vmx file. Power off the VM and add the line:
bios.hddOrder=scsi0:0 to force the VM to boot from disk 0:0.