[root@kenneth ~]# hdparm -t /dev/sda

/dev/sda:
 Timing buffered disk reads:  262 MB in  3.02 seconds =  86.76 MB/sec
[root@kenneth ~]# /sbin/blockdev --setra 8192 /dev/sda
[root@kenneth ~]# hdparm -t /dev/sda

/dev/sda:
 Timing buffered disk reads:  470 MB in  3.01 seconds = 155.96 MB/sec