System information

Tuning I/O Performance 161

Tuning I/O Performance

I/O scheduling controls how input/output operations will be submitted to storage.

SUSE Linux Enterprise Server offers various I/O algorithms—called elevators—

suiting different workloads. Elevators can help to reduce seek operations, can priori-

tize I/O requests, or make sure, and I/O request is carried out before a given deadline.

Choosing the best suited I/O elevator not only depends on the workload, but on the

hardware, too. Single ATA disk systems, SSDs, RAID arrays, or network storage sys-

tems, for example, each require different tuning strategies.

13.1 Switching I/O Scheduling

SUSE Linux Enterprise Server lets you set a default I/O scheduler at boot-time, which

can be changed on the fly per block device. This makes it possible to set different al-

gorithms for e.g. the device hosting the system partition and the device hosting a data-

base.

By default the CFQ (Completely Fair Queuing) scheduler is used. Change this default

by entering the boot parameter

elevator=SCHEDULER

where SCHEDULER is one of cfq, noop, or deadline. See Section13.2, “Avail-

able I/O Elevators” (page162) for details.

To change the elevator for a specific device in the running system, run the following

command: