[squid-dev] [RFC] CRUSH peer selection method

[Loic Dachary]

On 04/19/2017 03:53 PM, Alex Rousskov wrote:
> On 04/18/2017 01:00 AM, Loic Dachary wrote:
> 
>> It turns out [CARP] performs as well as CRUSH
> 
> 
> On 04/19/2017 06:51 AM, Loic Dachary wrote:
> 
>> I found one use case where CRUSH behaves significantly better than CARP.
> 
> 
> FYI, here is how the above statements can be interpreted: "It is all a
> mystery to us. Sometimes CRUSH and CARP are about the same, sometimes
> one of the algorithms wins, but we cannot tell you when to use CARP or
> CRUSH because we cannot generalize their differences. Our experimental
> data does not suggest any clear trends."
> 
> That unpredictability may be the nature of the beast, of course, but I
> currently see no reasoning or experimental data to confirm or deny that
> sad hypothesis.

CRUSH is no mystery and has been extensively described at http://www.crss.ucsc.edu/media/papers/weil-sc06.pdf CARP is somewhat mysterious because https://tools.ietf.org/html/draft-vinod-carp-v1-03 provides formulas with no rationale explaining why they are necessary.

I did the best I could to show why it would be useful to have a peer selection method based on CRUSH. I'm also offering to write this implementation.

Please let me know if that is of interest to Squid

Cheers

-- 
Loïc Dachary, Artisan Logiciel Libre