Hi ThompsG.. thanks for the feedback..
It was a case that the SCSI ID was changing, despite me going back into the VM and setting the C:\ disk to 0:0 and D:\ disk to 0:1
Using your line of thinking I am back in action.. never crossed my mind to disconnect the disk and retry...but the first try to reconnect didn't work!
This had me scratching my head for a bit..So I'm wondering if I've found a 'feature' arising from a unique sequence of events ??
This VM for a new deployment of SCCM. I use PowerCLI and used a customization spec to deploy the VM.. the OS gets setup with hostname, etc.
Standard practice would be that if I provide a vmhostname in the powershell code: "New-VM -Name $vmhostname -Template $mySourceTemplate...." then the VM will get created as say 'server1' with the hostname 'server1'.
So VM was deployed, joined to the domain (as 'server1') with just the C:\ drive, windows updates deployed.
After the updates where deployed, I renamed the VM , adding a suffix '-sccm' suffix to the VM name. (We add a suffix so others can quickly see what the VM does, given we've a lot of VMs). I then added the disk to the VM (I don't think I actually powered down the VM when I did the rename & disk addition).
I then added some windows features and SCCM roles to the sever - which added content to the second (d:\) disk. I then rebooted the VM and discovered the missing OS scenario.
The C:\ disk (disk 0:0) had the file name 'vmname.vmdk' and when I checked this morning (prior to disconnecting the disk) the D:\ disk (0:1) was called 'vmname-sccm.vmdk' (i.e. it got the filename with the new name suffix added and not 'vmname_1.vmdk' which is what I've seen with other VMs).
So I wonder is there some code/function that assumes the 0:0 disk is the vmdk file which has the name which matches the vmname
(i.e. as I'd changed the vm name to 'server1-sccm' and there was a disk present called 'server1-sccm.vmdk' that it assumed that this was disk 0:0)
This morning I powered down the VM, disconnected the D: disk (after my first attempt to add didn't work), I then renamed the disk to servername_1.vmdk (and did the same for the '-ctk.vmdk' file (not sure if i needed to do that).. and powered up the VM with just the C: drive, then added the second disk (which I'd renamed) , made sure that windows disk manager was showing C: as the boot disk, and rebooted the host.. bingo, back in business !