6.3. I/O Scheduling with Red Hat Enterprise Linux as a Virtualization Guest
- Red Hat Enterprise Linux guests often benefit greatly from the
noopscheduler allows the host machine or hypervisor to optimize the input/output requests. The
noopscheduler can combine small requests from the guest operating system into larger requests, before handing the I/O to the hypervisor. However,
nooptries to use the fewest number of CPU cycles in the guest for I/O scheduling. The host/hypervisor has an overview of the requests of all guests and uses a separate strategy for handling I/O.
NoteFor Red Hat Enterprise Linux 7.2 and newer,
noopimplicitly. This is because it uses
- Depending on the workload I/O and how storage devices are attached, schedulers like
deadlinecan be more advantageous. Performance testing is required to verify which scheduler is the best one to use in each situation.All scheduler tuning should be tested under normal operating conditions, as synthetic benchmarks typically do not accurately compare performance of systems using shared resources in virtual environments.
- Guests using storage accessed by iSCSI, SR-IOV, or physical device passthrough should not use the
noopscheduler. These methods do not allow the host to optimize I/O requests to the underlying physical device.
deadlinein the guest virtual machine.