Hyper-V Generation 1 vs. Generation 2: What’s the Difference?

As technology grows along with time, virtualization vendors are also innovating and modernizing the solutions they deliver to catch up with users’ new interests. For example, Hyper-V, one of the most popular virtual platforms that’s being used worldwide, also provides 2 generations of VMs for us to choose from.

To start off with, in the world of Hyper-V, the birth of Generation 2 doesn’t mean the decay of Generation 1, and both are actively being used to fit different operational requirements in the data center. Despite there being some kind of improvement in Gen 2, it also gives up something that Gen 1 supports. In this blog, we’re going to make a brief comparison between them by boot options, guest OS support and multiple other notable factors to help you make better decisions—if you wonder which one is better for your IT workloads.

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BIOS support

BIOS is the basic input/output system software used for startup and hardware configuration. Generation 1 Hyper-V VMs can only be booted from MBR (Master Boot Record) virtual hard disks. Generation 2 Hyper-V, on the other hand, support UEFI BIOS and GPT, which is makes extension of supported devices and features. Gen 2 can also enable Secure Boot because of the UEFI support, a feature that prevent unauthorized modification of bootloaders and main system files.

PXE boot option

Both Gen 1 and Gen 2 Hyper-V support PXE (pre-boot execution environment) boot, a feature that works to boot the network, but they achieve this through different ways. You need emulated legacy network adapter for PXE boot in Gen 1 VMs, while in Gen 2 the process can be more direct and effortless thanks to the support of UEFI.

IDE/SCSI Controllers

IDE and SCSI controllers are 2 virtual storage controllers Hyper-V provide. Gen 1 VMs can only be booted from IDE disks by default, or you can choose to make an extra installation of Hyper-V Integration Services to boot from SCSI disks. As for Gen 2 VMs, there’re no more IDE controllers, and you can directly boot from SCSI.

Supported guest OS

Gen 1 VMs play higher compatibility of guest OS. It supports all Windows and Linux versions without limitations, while Gen 2 only support 64-bit Windows 8 and Windows Server 2012 and above versions, and a very limited range of Linux OS.

VHD/VHDX virtual disk support

VHD and VHDX are the 2 virtual disk formats used by Hyper-V. VHD files are compatible with earlier versions of Windows Server, while VHDX owns a higher virtual disk storage capacity. Gen 1 supports both VHD and VHDX files, and Gen 2 only supports VHDX.

Overall performance

Based on the actual user experience of Hyper-V of 2 generations, we can come to the concise conclusion that the major performance improvement of Gen 2 VMs are on the boot speed and security side. Other than these two, there’s no profound performance gap between Gen 1 and Gen 2 VMs in actual work cases.