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
- Boot from SCSI virtual hard drive
- PXE boot option
- Secure Boot
- Faster boot time and installation for guest operating system
- Only 64 bit operating systems
- VHDX boot volume can support up to 64 TB