Answer by H_TeXMeX_H

H_TeXMeX_H — Sat, 24 Apr 2010 19:32:24 -0400

I would like to mention that it also depends a lot on what filesystem you use, as well as workload. With JFS for example the deadline I/O scheduler is way better than any of the others for some unknown or unexplained reason, while CFQ causes lags and stuttering audio and video when playing movies. Try each of them out and see which works best.

Answer by Prasad

Prasad — Fri, 23 Apr 2010 14:07:10 -0400

The noop scheduler is actually for devices which have their own mechanism of handling the data read/writes. It could be in-built as a logic on the device itself,for example a SAN environment. The other schedulers like CFQ,deadline and anticipatory are logic built on the linux kernel itself, which means kernel decides how a I/O request should be handled and when the dirty buffers be written to the disk etc. These scheduler's logic are different from each other. There is no best scheduler, they are meant for different type of work loads.

You can simply switch the schedulers on the fly:

Example: (as root) To use "deadline" scheduler:-

# sync

# echo "deadline" > /sys/block/sda/queue/scheduler

I'm not sure if SSD drives have the intelligence to handle I/O requests. But I can suggest you do a test read/write of huge data size with each scheduler and fins which suits you the best.

Hope this helps.

Answers to: No-Op I/O VS CFQ schedulers

Answer by H_TeXMeX_H

Answer by Prasad