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From Theo Hultberg <t...@iconara.net>
Subject Re: Why so many vnodes?
Date Mon, 10 Jun 2013 17:55:46 GMT
I'm not sure I follow what you mean, or if I've misunderstood what
Cassandra is telling me. Each node has 256 vnodes (or tokens, as the
prefered name seems to be). When I run `nodetool status` each node is
reported as having 256 vnodes, regardless of how many nodes are in the
cluster. A single node cluster has 256 vnodes on the single node, a six
node cluster has 256 nodes on each machine, making 1590 vnodes in total.
When I run `SELECT tokens FROM system.peers` or `nodetool ring` each node
lists 256 tokens.

This is different from how it works in Riak and Voldemort, if I'm not
mistaken, and that is the source of my confusion.

T#


On Mon, Jun 10, 2013 at 4:54 PM, Milind Parikh <milindparikh@gmail.com>wrote:

> There are n vnodes regardless of the size of the physical cluster.
> Regards
> Milind
> On Jun 10, 2013 7:48 AM, "Theo Hultberg" <theo@iconara.net> wrote:
>
>> Hi,
>>
>> The default number of vnodes is 256, is there any significance in this
>> number? Since Cassandra's vnodes don't work like for example Riak's, where
>> there is a fixed number of vnodes distributed evenly over the nodes, why so
>> many? Even with a moderately sized cluster you get thousands of slices.
>> Does this matter? If your cluster grows to over thirty machines and you
>> start looking at ten thousand slices, would that be a problem? I guess trat
>> traversing a list of a thousand or ten thousand slices to find where a
>> token lives isn't a huge problem, but are there any other up or downsides
>> to having a small or large number of vnodes per node?
>>
>> I understand the benefits for splitting up the ring into pieces, for
>> example to be able to stream data from more nodes when bootstrapping a new
>> one, but that works even if each node only has say 32 vnodes (unless your
>> cluster is truly huge).
>>
>> yours,
>> Theo
>>
>

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