Tuning device-level read-ahead

• For device "sda", the read-ahead value can be seen by:

       # cat /sys/block/sda/queue/read_ahead_kb 
       128
       

• This value is in KB.
• We can change it to another value - lets try setting it to 256KB:

       # echo 256 > /sys/block/sda/queue/read_ahead_kb
       # cat /sys/block/sda/queue/read_ahead_kb
       256
       

• To disable read-ahead - set the value to 0.

Originally written by guy keren