Windows Server 2012 R2 Hyper-V – Generation 2 Virtual Machines

When creating a new virtual machine on WS2012 R2 Hyper-V, you will have the option to create a Generation 1 virtual machine (what has always existed in Hyper-V as just a VM) or a Generation 2 (G2) VM.  The G2 VM has the following features:

  • It is free of legacy hardware.  The VM no longer attempts to pretend to be a physical machine.
  • All devices run as synthetic VM Bus “hardware”
  • Your VM will boot from a SCSI controller.  This means the attached OS VHDX can take advantage of SCSI/VHDX features such as TRIM, UNMAP, and hot resizing.
  • The synthetic NIC can boot from the network using PXE
  • The VM uses UEFI instead of BIOS.  That means it can do secure boot from GPT partitions.
  • VM boots will be around 20% faster (think VDI boot storm).  OS installs will be around 50% faster.  But normal day-day operations won’t be much different.
  • There are fewer devices in a VM so there are fewer VM settings


G1 VM Device Manager (left) versus G2 Device Manger (right)

I don’t expect that many people will deploy the G2 VM on WS2012 R2 as the norm, but I could be wrong.  Why?

  • You cannot convert a VM between G1 and G2.  That is a UEFI and MBT/GPT thing.
  • You must use 64-bit editions of Windows 8/Windows Server 2012 or later.


Niklas Akerlund has blogged about how he has successfully converted a Gen1 VM into a Gen2 VM using Double-Take Move.

5 thoughts on “Windows Server 2012 R2 Hyper-V – Generation 2 Virtual Machines”

  1. I tried to run Windows 8.1 on Hyper-V cluster 2012 R2 – G2 and G1. The G2 VM is much slower then G1, a specially with RDP(S) connection. Any thoughts?

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