Drive Tuning

Tuning the I/O Scheduler

If HDDs are used as data drives, the deadline policy (default) is recommended.

Run following commands to modify the scheduling policy and view the modification result:

echo deadline > /sys/block/sdx/queue/scheduler
cat /sys/block/sdx/queue/scheduler

Kernel Parameter Configuration

• If there are a large number of sequential I/O reads, you are advised to adjust the prefetch size (set the size based on site requirements).

  echo 16384 > /sys/block/sdx/queue/read_ahead_kb

• If there are a large number of I/O writes, you are advised to adjust dirty parameters to increase the dirty data refresh frequency and avoid triggering the I/O synchronization flush mechanism.

  echo 500 > /proc/sys/vm/dirty_expire_centisecs
  echo 100 > /proc/sys/vm/dirty_writeback_centisecs
  echo 90 > /proc/sys/vm/dirty_ratio
  echo 5 > /proc/sys/vm/dirty_background_ratio