topic Re: Load Balancing policies in Disk Enclosures

Load Balancing policies

Feljav — Tue, 03 Jul 2007 09:29:44 GMT

Multi-path solution are able to detect multiple paths to each logical device.There various load balancing policies. What is the meaning of them?
Round Robin-
Shortest Queue-
Least I/O -
ALB -

Re: Load Balancing policies

Torsten. — Tue, 03 Jul 2007 09:35:18 GMT

Hi,

start reading here
http://en.wikipedia.org/wiki/Round-robin_scheduling
or here
http://en.wikipedia.org/wiki/Scheduling_algorithm

Re: Load Balancing policies

Owen_15 — Thu, 19 Jul 2007 10:12:43 GMT

Hi Feljav,

Round Robin: Equally distributes I/O among the paths in round-robin sequence. Rotates through all available paths on the active controller with equal distribution to each.

Shortest Queue: This algorithm schedules the I/O on the path that has the shortest queue.

Least I/O: Uses the available path on the active controller that has the fewest outstanding I/O requests.

ALB: not sure which variant of load balancing you are refering to.

There are lots of different algorithms out there with their subtle differences, but in general the default one is Round Robin.

Regards
Owen

Re: Load Balancing policies

Uwe Zessin — Thu, 19 Jul 2007 11:55:39 GMT

ALB is short for "Adaptive Load Balance", but the MPIO documentation does not contain much helpful information:

""HP MPIO EVA DSM implements array specific algorithms which make use of certain features supported by the disk arrays, to deliver better performance for host I/O requests. This Adaptive Load Balance (ALB) setting is supported on a per logical unit basis and works in conjunction with the load balancing policies supported by the DSM viz., Round Robin, Shortest Queue Requests, Shortest Queue Bytes and Shortest Queue Service Time.
""

Maybe it is some optimization to skip the non-performance / non-optimized paths through a proxy controller.