21.2. Tuning Considerations

Any I/O scheduler should perform well with most SSDs. However, as with any other storage type, Red Hat recommends benchmarking to determine the optimal configuration for a given workload.

When using SSDs, Red Hat advises changing the I/O scheduler only for benchmarking particular workloads. For more information about the different types of I/O schedulers, refer to the I/O Tuning Guide (also provided by Red Hat). The following kernel document also contains instructions on how to switch between I/O schedulers:

/usr/share/doc/kernel-version/Documentation/block/switching-sched.txt

Like the I/O scheduler, virtual memory (VM) subsystem requires no special tuning. Given the fast nature of I/O on SSD, it should be possible to turn down the vm_dirty_background_ratio and vm_dirty_ratio settings, as increased write-out activity should not negatively impact the latency of other operations on the disk. However, this can generate more overall I/O and so is not generally recommended without workload-specific testing.

An SSD can also be used as a swap device, and is likely to produce good page-out/page-in performance.