What is VirtIO?
VirtIO is the native paravirtual storage controller platform within the KVM hypervisor.
Standard virtualization uses a basic IDE-style virtual hard drive controller implementation that is compatible across all types of physical hardware and operating systems. This basic virtual hardware emulation is widely compatible but provides least common denominator features and is not optimized for performance. Since the IDE standard allows for only four disks, protected systems virtualized in this fashion are also limited to four disk volumes.
Enabling VirtIO provides for faster disk IO performance by leveraging storage controller drivers specifically optimized for operating in the virtual environment.
- VirtIO emulates a SCSI or SATA disk controller interface, which has no restrictions on the number of disks that may be attached.
- VirtIO is required for protected systems that have more than four disk volumes, to be able to access all disks.
- VirtIO is also required for protected systems which have physical disk drives formatted in native 4K block sizes. Virtual 4K block devices can only be created within KVM using VirtIO storage controllers.
VirtIO is enabled by checking the Use VirtIO option when starting a virtual machine.
Storage controller drivers for VirtIO are installed automatically into the protected system image during the P2V (Physical to Virtual) conversion process performed when starting the VM.
VirtIO may also be selected to be used when enabling nightly Boot VM AutoVerify checks.
Note: For Protected Systems experiencing AutoVerify failures due to chkdsk timeouts, it is recommended to enable VirtIO for Boot VM Checks to increase disk IO performance during the filesystem checks.