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From Sam Overton <>
Subject Re: RFC: Cassandra Virtual Nodes
Date Mon, 19 Mar 2012 20:15:47 GMT
On 19 March 2012 09:23, Radim Kolar <> wrote:
>> Hi Radim,
>> The number of virtual nodes for each host would be configurable by the
>> user, in much the same way that initial_token is configurable now. A host
>> taking a larger number of virtual nodes (tokens) would have
>> proportionately
>> more of the data. This is how we anticipate support for heterogeneity in
>> cluster hardware.
> Yes, but this is good only for random partitioner. For ordered you need to
> be able split token space on highly loaded servers. With virtual tokens it
> will move load to random node.
> What if random node will be also hotspot node? Administration will be more
> difficult because you don't know where workload lands after you reduce
> number of tokens held by node.

For OPP we envisage an external management process performing active
load balancing. The initial token assignment would be random within
some user-specified range corresponding to the range of their keys.
The load would then be monitored and hot-spots would be moved by
reassigning virtual nodes to lightly loaded machines, or introducing
new tokens into hot ranges. It makes sense that this would not be a
manual process, but there would certainly be more control than just
increasing or decreasing the number of tokens assigned to a node.

Sam Overton
Acunu | | @acunu

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