incubator-cassandra-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Sam Overton <...@acunu.com>
Subject Re: RFC: Cassandra Virtual Nodes
Date Mon, 19 Mar 2012 20:15:47 GMT
On 19 March 2012 09:23, Radim Kolar <hsn@filez.com> 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 | http://www.acunu.com | @acunu

Mime
View raw message