In Linux, it simple to change a hard drives I/O scheduler. Why would you want to do this? Simple, performance. Some file systems work better with a scheduler other than the default.
To set a hard drives I/O scheduler.
echo "schedular_name" > /sys/block/<drive>/queue/scheduler
# echo "deadline" > /sys/block/sdc/queue/scheduler # cat /sys/block/sdc/queue/scheduler noop anticipatory [deadline] cfq