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 <[email protected]>wrote: > http://www.mail-archive.com/[email protected]/msg26528.html > > From: Alain RODRIGUEZ <[email protected]> > Reply-To: "[email protected]" <[email protected]> > Date: Friday, January 4, 2013 6:00 AM > To: "[email protected]" <[email protected]> > 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 > > ---------------------------------- > Join Barracuda Networks in the fight against hunger. > To learn how you can help in your community, please visit: > http://on.fb.me/UAdL4f > >
