Hyper-V 2012 R2 Generation 1 vs Generation 2 VMs

 

In earlier versions of Hyper-V, It was not possible to boot a virtual machine from a SCSI virtual hard drive .It was also not possible to copy files from host to virtual machine without having a network connection in the virtual machine .

In virtual machines running 2012 and earlier, the Hyper-V BIOS only supported legacy drives such as IDE controller and legacy network cards.

Starting with windows server 2012 R2, there are two types of Hyper-V boot architectures available.

i.e., Hyper-V BIOS and Hyper v unified extensible firmware interface BIOS, virtual machine created with Generation 1 supports legacy drivers and uses Hyper-V BIOS-based architecture. Hyper-V BIOS-based virtual machines can only initialize IDE Controller for Operating System to initialize a file system, which is shown in the below image

On the other hand, a virtual machine created with Generation 2 supports  UEFI-based architecture, in which a subset of Integration Service components has been included to allow SCSI Controller to initialize before the Operating System starts loading. This is shown in the above image:

Benefits of Generation 2 VMS

  1. Boot from SCSI virtual hard drive
  2. PXE boot option
  3. Secure Boot
  4. Faster boot time and installation for guest operating system
  5. Only 64 bit operating systems
  6. VHDX boot volume can support up to 64 TB