AWS HVM Vs PVM

Well, in one of our previous posts we had seen quite some interesting facts about the basics of virtualization. If you missed that, Click the link here to visit the page to understand Virtualization.
When dealing with EC2s and Selecting AMIs for EC2 deployment, you would come across many variants/Distros of different operating systems. When selecting them, there are many options available for you to choose from. However, one important factor to be looked at when choosing the OS for your Instance is to check if your AMI is an HVM (Hardware Virtualized Machine) or PVM(ParaVirtual Machine) Image.

Hardware Virtual Machine AMIs:

HVM AMIs use the Master Boot Record to boot from the root block device of your image. This virtualization type provides the ability to run an operating system directly on top of a virtual machine without any modification as if it were run on bare-metal hardware. HVM guests can take advantage of hardware extensions that provide fast access to the underlying hardware on the host system.  All Instance types on the AWS EC2, support the HVM images.

Paravirtual Machine AMIs:

PV AMIs boot with a special boot loader called PV-GRUB, which starts the boot cycle and then chain loads the kernel specified in the menu.lst file on your image.  They cannot take advantage of special hardware extensions such as enhanced networking or GPU processing. Not all EC2 instances on the AWS support the PVM AMIs. The PVM does have an advantage over HVM, by improved performance with storage and network operations than HVM guests because they could leverage special drivers for I/O that avoided the overhead of emulating network and disk hardware, whereas HVM guests had to translate these instructions to emulated hardware.