[OpenAFS] OpenAFS client and load balancing...

[Jeffrey Altman]

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Rodney:

You did not specify the Windows client but based upon your past
inquiries I assume that is what you are referring to.   The Windows
client currently has no code implemented to gather metrics of
bandwidth, round trip times, etc.   Simply adding this code in a
manner that does not impact performance in a significant way would
be challenging.   I certainly would not want to increasing the
amount of mutex protected access to process global resources.

Once the data was obtained with an appropriate set of weighted averages
it would be possible to devise an algorithm.   Although I am not sure
that it would be feasible to produce a single algorithm that improved
your situation without potentially hurthing someone elses.

Jeffrey Altman


Rodney M Dyer wrote:

> Hi,
> 
> Would it be possible to put an algorithm for load balancing into the AFS
> client such that the client would select the next server in its
> preference list if the data stream fed to it by the server was "too
> slow"?  Then, every few minutes, or hours, re-try the primary
> preferences again and switch back.
> 
> Basically what I'm refering to here is an adaptive real-time algorithm
> where the client would upon startup keep a running history of its data
> bandwidth rate and when that rate dramatically falls for short periods
> of time, the client just switches to the next available server.
> 
> The current implementation of AFS server preferences for fail-over
> doesn't help to eliminate bottlenecks of caused by many machines hitting
> a single server and loading it down.
> 
> Why this would be needed?  At our site we have an algorithm that sets
> server preferences a special way.  Basically we set all the client
> machines in one building to randomize their preferences for all the
> servers in that building, then choose the other buildings and the
> servers in them at random, next in the list.  This is generally not a
> problem except in the case where you have lots of clients in a building,
> and few servers, or in our case 1 server.  However in our case, due to
> space limitations, we don't have room for more servers.  Now of course I
> could change our preferences setting algorithm for a "special case"
> where there are few servers for a building, howevever I don't want the
> client to always use another buildings servers, except in severe cases
> of loading.
> 
> How complex would this be to add to the client?
> 
> Rodney
> 
> _______________________________________________
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