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We are in the middle of a big VMware to Hyper-V migration at the moment. Part of this process is going to be changing some of our existing ESXi servers to Hyper-V. These ESXi servers don't have hard drives installed, ESXi is installed on a 1GB SD card. Of course, this is too small for Windows and installing Hyper-V server onto a USB device appears to be more trouble than it's worth.

As I'm sure you're aware, Windows 2012 can now function as an iSCSI target server. It uses VHDs as its LUNs. From what I can gather from Microsoft's documentation, you can create a "Master" VHD and from that master, create multiple differencing VHDs from it and attach each of those VHDs as iSCSI Virtual disks for different servers to use.

So I've done just that. I've created a master VHD, attached it to to the Windows iSCSI target, installed Windows 2012 on it, sysprepped it and detached it from the target. I've then created three differencing VHDs from it and attached those differencing VHDs to the iSCSI target. Those VHDs are called diff1, diff2 and diff3. I've used Diskpart to create these VHDs (create vdisk file=d:\iscsifiles\diff1.vhd parent=d:\iscsifiles\parent.vhd). I've then attempted to boot a server from each one.

The server using diff1 booted perfectly. The ones booted from diff2 and diff3 bluescreened with a inaccessible_boot_device error. The servers are all identical (Dell PowerEdge M610s, Broadcom 10GBe nics with iSCSI boot enabled). diff2 and diff3 grow by about 6MB, according to the timestamp on the file, the master VHD hasn't changed since I sysprepped it.

So what have I missed?

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OK, I think I've cracked it. The problem was that I was assigning multiple VHDs to the same iSCSI target and giving each VHD a different LUN number. Creating a separate target for each VHD allows each server to boot the OS. You live and learn! –  Norphus Jul 11 '13 at 12:08
    
Hey if you wouldnt mind helping me out with a very similar senario that i am trying to get working i would appreciate it. Maybe you can help over skype or google hang outs for 2 mins? if so message me at ddarvish at gmail dot com. –  user201534 Dec 5 '13 at 9:00
    
Hello @ddarvish and welcome to Server Fault! If you have a question, you are welcome to post a new question using the "Ask Question" button. Asking people to contact you off-site is strongly discouraged since other people may have your exact problem. –  Peter Grace Dec 5 '13 at 11:42

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