Here is a quick how to to change IO Scheduler/elevator on a Linux server and to get some performance enhancement (courtesy from Linbit).
echo deadline|tee /sys/block/sd*/queue/scheduler
echo 0 | tee /sys/block/sd*/queue/iosched/front_merges
echo 150 | tee /sys/block/sd*/queue/iosched/read_expire
echo 1500 | tee /sys/block/sd*/queue/iosched/write_expire
More can be read here and here to find out more why I choose deadline.