Linux I/O Disk Schedulers

Available options are generally:

[1] Noop - It is a FIFO based simple scheduler

[2] Completely Fair Queuing [cfq]

[3] Anticipatory - older scheduler, now replaced by cfq

[4] Deadline - Tries to guarantee a service time

Check Current Scheduler

All available schedulers are listed and the current scheduler is placed within square brackets:

$ cat /sys/block/${DEV}/queue/scheduler
noop anticipatory [deadline] cfq

Change Scheduler for a Device

As a sample, changing the scheduler to noop:

$ echo noop > /sys/block/${DEV}/queue/scheduler
$ cat /sys/block/${DEV}/queue/scheduler
[noop] anticipatory deadline cfq

This change does not persist across reboots. The echo statement may be added to /etc/rc.local in order to execute it after every reboot.

Change Scheduler for all Disks

Instead of changing scheduler for a particular device, if it is desired to change the scheduler for all disks on the system, then elevator=<scheduler> can be added to the boot options in /etc/grub.conf.