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From Manu Zhang <owenzhang1...@gmail.com>
Subject Re: num_tokens - virtual nodes
Date Sat, 05 Jan 2013 00:57:13 GMT
https://www.youtube.com/watch?v=GddZ3pXiDys&list=PLC5E3906433F5A165&index=28
This
video of Cassandra summit 2012 has mentioned the use of 256 tokens by
default (though it's no longer in the conf/cassandra.yaml). I remember that
more tokens could lead to more disk seeks or something. I think 256 is an
empirical number based on tests of the speaker.

Here are two more related articles that you want to read.
http://www.acunu.com/2/post/2012/07/virtual-nodes-strategies.html
http://www.acunu.com/2/post/2012/10/improving-cassandras-uptime-with-virtual-nodes.html



On Sat, Jan 5, 2013 at 12:18 AM, Michael Kjellman
<mkjellman@barracuda.com>wrote:

> http://www.mail-archive.com/user@cassandra.apache.org/msg26528.html
>
> From: Alain RODRIGUEZ <arodrime@gmail.com>
> Reply-To: "user@cassandra.apache.org" <user@cassandra.apache.org>
> Date: Friday, January 4, 2013 6:00 AM
> To: "user@cassandra.apache.org" <user@cassandra.apache.org>
> Subject: num_tokens - virtual nodes
>
> Hi,
>
> I just discover the vnodes new feature described here:
> http://www.datastax.com/dev/blog/virtual-nodes-in-cassandra-1-2
>
> In the post above, Brandon says "If you’d like to upgrade an installation
> to virtual nodes, that’s possible too, but I’ll save that for a later
> post". Does this post now exist somewhere ?
>
> From the cassandra.yaml:
>
> # If you already have a cluster with 1 token per node, and wish to migrate
> to
> # multiple tokens per node, see
> http://wiki.apache.org/cassandra/Operations
> # num_tokens: 256
>
> I see no reference to vnodes or num_tokens on this wiki.
>
> So, how to switch from "physical" nodes to vnodes ?
>
> This is useful only if your number of nodes is greater than the RF, right ?
>
> Why 256 token by default ? Where this value come from ?
>
> Is there more advantage / disadvantage of using vnodes that improving the
> internodes data streaming by increasing the number of data sources ?
>
> Alain
>
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