Better server selection client code?

Steven Grimm sgrimm at
Mon Nov 6 17:49:11 UTC 2006

Jeetendra Mirchandani wrote:
> Consistent hashing has a shortcoming of not distributing load evenly.
> Some cases require the number of servers to be a power of 2 always to
> have perfect distribution of load!
> The paper mentions of keeping more than one copy to counter this. But
> then, keeping more copies is equivalent to loosing half my machines :-O

The paper suggests putting each server in a number of random locations 
around the unit circle to counter that problem. If you have two servers 
and each one has, say, 50 positions on the unit circle, then you will 
get load distribution that's just as good as if you had 100 servers each 
with one position on the circle.

Brad's sample implementation does that, with the added twist of 
replacing "random" with "deterministic based on the server address" 
which of course is necessary because each client will be computing its 
own unit circle and they all need to match.


More information about the memcached mailing list