6.3. I/O Scheduling with Red Hat Enterprise Linux as a Virtualization Guest

You can use I/O scheduling on a Red Hat Enterprise Linux guest virtual machine, regardless of the hypervisor on which the guest is running. The following is a list of benefits and issues that should be considered:

In virtualized environments, sometimes it is not beneficial to schedule I/O on both the host and guest layers. If multiple guests use storage on a filesystem or block device managed by the host operating system, the host may be able to schedule I/O more efficiently because it is aware of requests from all guests and knows the physical layout of storage, which may not map linearly to the guests' virtual storage. On the other hand, depending on the workload, it may be beneficial to use a scheduler like deadline in the guest virtual machine.