So I learned that since Red Hat 6 it is possible to choose between 3 algorithms for loadbalancing between different paths to my FC-SAN, the default dumb round-robin - and new - queue-length and service-time.

I have been searching for a long time now for a performance-comparison for different values for path_selector in a multibus-configuration, but I was not able to find any information based on real experience. I did not even find an assumption of what performs better in which situations.

Does anyone have done some real performance-testing on this question? Or information about resources I was not able to find?


I have a few servers that use queue-length and they haven't had any problems. In general, though, there's not much to optimize in terms of multipath. We still use basic round-robin for the vast majority of our servers -- it's a well-known setup with little unknown risk, and the performance upside for queue or service time based multipathing, at least in my shop, is small.

Do you have a specific problem you're trying to address? Or are you just making sure you're set up as well as possible?


In the meantime, I did some tests, the differences are in fact marginal:

                        round-robin queue-length    service-time
Write char KB/sec       872         884             876
Write block KB/sec      327345      331218          330533
Rewrite KB/sec          144384      144102          141393
Read char KB/sec        3714        3900            3485
Read block KB/sec       363308      349765          360518
Random Seeks count/sec  19          18  

I used bonnie++ on an ext4-filesystem.

  • The difference may not even be attributable to the multipath setup. – Basil Feb 26 '15 at 17:55

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.