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From Jonathan Ellis <jbel...@gmail.com>
Subject Re: Ring management and load balance
Date Thu, 25 Mar 2010 15:56:23 GMT
The advantage to doing it the way Cassandra does is that you can keep
keys sorted with OrderPreservingPartitioner for range scans.  grabbing
one token of many from each node in the ring would prohibit that.

So we rely on active load balancing to get to a "good enough" balance,
say within 50%.  It doesn't need to be perfect.

On Thu, Mar 25, 2010 at 10:37 AM, Daniel Kluesing <dk@bluekai.com> wrote:
> I wanted to check my understanding of the load balance operation. Let's say I have 5
nodes, each of them has been assigned at startup 1/5 of the ring, and the load is equal across
them (say using random partitioner). The load on the cluster gets high, so I add a sixth server.
During bootstrap, the new server will pick the existing server with the highest load, and
take half the load from that server. After boot strap, I would end up with 4 servers with
1/5 of the ring each, and 2 servers with 1/10 of the ring each - is this correct? I'll get
hotspots unless I double the number of nodes?
>
> Really I would want adding a sixth server to result in six machines with 1/6 of the load
taken evenly from the existing nodes.  If I understand - and correct me if I'm wrong -, the
core of this is that each server is assigned one token, while in a system like dynamo, a server
is assigned multiple tokens around the ring. Is there any benefit to only assigning one token?
Has anyone worked on assigning a server multiple tokens, or is there some other unrelated
way to get more even load distribution when adding a node?
>

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