I have good news and bad. The good news is I have a nice coffee. The bad news is it's pretty difficult to have some nodes with less load.
In a cluster with 5 nodes and RF 3 each node holds the following token ranges. node1: node 1, 5 and 4 node 2: node 2, 1, 5 node 3: node 3, 2, 1 node 4: node 4, 3, 2 node 5: node 5, 4, 3 The load on each node is it's token range, and those of the preceding RF-1 nodes. e.g. In a balanced ring of 5 nodes with RF 3 each node has 20 % of the token ring and 60% of the total load. if you split the token ring is split like this below each node has the total load shown after the / node 1: 12.5 % / 50% node 2: 25 % / 62.5% node 3: 25 % / 62.5% node 4: 12.5 % / 62.5% node 5: 25% / 62.5 % Only node 1 gets a small amount less. Try a different approach… node 1: 12.5 % / 62.5% node 2: 12.5 % / 50% node 3: 25 % / 50% node 4: 25 % / 62.5% node 5: 25 % / 75.5 % That's even worse. David is right to use nodetool move. It's a good idea to update the initial tokens in the yaml (or your ops condif) after the fact even though they are not used. Hope that helps. ----------------- Aaron Morton Freelance Developer @aaronmorton http://www.thelastpickle.com On 12/01/2012, at 8:41 AM, David McNelis wrote: > Daning, > > You can see how to do this basic sort of thing on the Wiki's operations page > ( http://wiki.apache.org/cassandra/Operations ) > > In short, you'll want to run: > nodetool -h hostname move newtoken > > Then, once you've update each of your tokens that you want to move, you'll > want to run > nodetool -h hostname cleanup > > That will remove the no-longer necessary tokens from your smaller machines. > > Please note that someone else may have some better insights than I into > whether or not your strategy is going to be effective. On the surface I > think what you are doing is logical, but I'm unsure of the actual > performance gains you'll see. > > David > > On Wed, Jan 11, 2012 at 1:32 PM, Daning Wang <dan...@netseer.com> wrote: > Hi All, > > We have 5 nodes cluster(on 0.8.6), but two machines are slower and have less > memory, so the performance was not good on those two machines for large > volume traffic.I want to move some data from slower machine to faster machine > to ease some load, the token ring will not be equally balanced. > > I am thinking the following steps, > > 1. modify cassandra.yaml to change the initial token. > 2. restart cassandra(don't need to auto-bootstrap, right?) > 3. then run nodetool repair,(or nodetool move?, not sure which one to use) > > > Is there any doc that has detailed steps about how to do this? > > Thanks in advance, > > Daning > >
