redhat man page for elvtune

ELVTUNE(8)						      System Manager's Manual							ELVTUNE(8)

NAME
       elvtune - I/O elevator tuner

SYNOPSIS
       elvtune [ -r r_lat ] [ -w w_lat ] [ -b b_max ] /dev/blkdev1 [ /dev/blkdev2 ...  ]

       elvtune -h

       elvtune -v

DESCRIPTION
       elvtune	allows	to  tune the I/O elevator per blockdevice queue basis. The tuning can be safely done at runtime. Tuning the elevator means
       being able to change disk performance and interactiveness. In the output of elvtune the address of the queue tuned will be shown and it can
       be  considered  as  a queue ID.	For example multiple partitions in the same harddisk will share the same queue and so tuning one partition
       will be like tuning the whole HD.

OPTIONS
       -r r_lat
	      set the max latency that the I/O scheduler will provide on each read.

       -w w_lat
	      set the max latency that the I/O scheduler will provide on each write.

       -b b_max
	      max coalescing factor allowed on writes when there are reads pending in the queue.

       -h     help.

       -v     version.

NOTE
       Actually the only fields tunable are those relative to the IO scheduler. It's not possible to select a one-way or two-way elevator yet.

       For logical blockdevices like LVM the tuning has to be done on the physical devices. Tuning the queue of the LVM logical device is useless.

RETURN VALUE
       0 on success and 1 on failure.

HISTORY
       Ioctls for tuning elevator behaviour were added in Linux 2.3.99-pre1.

AUTHORS
       Andrea Arcangeli <andrea@suse.de> SuSE

Version 1.0							   14 March 2000							ELVTUNE(8)