linux readahead
blockdev --getra /dev/sda
blockdev --setra 2048 /dev/sda
必须将其写入配置文件/etc/rc.local，否则重启就会失效。
[root@localhost ~]# echo '/sbin/blockdev --setra 2048 /dev/sda' >> /etc/rc.local
[root@localhost ~]# more /etc/rc.local
#!/bin/sh
#
# This script will be executed *after* all the other init scripts.
# You can put your own initialization stuff in here if you don't
# want to do the full Sys V style init stuff.
touch /var/lock/subsys/local
/sbin/blockdev --setra 2048 /dev/sda
[root@localhost ~]# echo '/sbin/blockdev --setra 2048 /dev/sdb' >> /etc/rc.local
[root@localhost ~]# more /etc/rc.local
#!/bin/sh
#
# This script will be executed *after* all the other init scripts.
# You can put your own initialization stuff in here if you don't
# want to do the full Sys V style init stuff.
touch /var/lock/subsys/local
/sbin/blockdev --setra 2048 /dev/sda
/sbin/blockdev --setra 2048 /dev/sdb
