Generation 2 virtual machines are Microsoft Hyper-V virtual servers that use the second generation of virtual hardware. Generation 2 virtual machines were introduced with Windows Server 2012 R2. Unlike the prior virtual machine platform, Generation 2 VMs are hypervisor aware, which means they do not rely on synthetic or emulated hardware.
Generation 2 VMs offer performance improvements over the prior virtual machine format, including faster boot ups. A Generation 2 VM uses virtual SCSI disks by default, whereas previous the previous version used IDE disks. However, this also means that Generation 2 VMs cannot access physical DVD drives. Generation 2 VMs also support Microsoft’s Secure Boot, which protects a machine against malicious boot code.
Generation 2 VMs can only host 64-bit editions of Windows Server 2012, 2012 R2 or Windows 8.1, and cannot be live migrated to prior operating system versions.