Use token-awareness so you don't have as much coordinator overhead. ml
On Mon, Feb 9, 2015 at 5:32 AM, Marcelo Valle (BLOOMBERG/ LONDON) < mvallemil...@bloomberg.net> wrote: > AFAIK, if you were using RF 3 in a 3 node cluster, so all your nodes had > all your data. > When the number of nodes started to grow, this assumption stopped being > true. > I think Cassandra will scale linearly from 9 nodes on, but comparing a > situation where all your nodes hold all your data is not really fair, as in > this situation Cassandra will behave as a database with two more replicas, > for reads. > I can be wrong, but this is my call. > > From: user@cassandra.apache.org > Subject: Re:Adding more nodes causes performance problem > > I have a cluster with 3 nodes, the only keyspace is with replication > factor of 3, > the application read/write UUID-keyed data. I use CQL (casssandra-python), > most writes are done by execute_async, most read are done with consistency > level of ONE, overall performance in this setup is better than I expected. > > Then I test 6-nodes cluster and 9-nodes. The performance (both read and > write) was getting worse and worse. Roughly speaking, 6-nodes is about 2~3 > times slower than 3-nodes, and 9-nodes is about 5~6 times slower than > 3-nodes. All tests were done with same data set, same test program, same > client machines, for multiple times. I'm running Cassandra 2.1.2 with > default > configuration. > > What I observed, is that with 6-nodes and 9-nodes, the Cassandra servers > were doing OK with IO, but CPU utilization was about 60%~70% higher than > 3-nodes. > > I'd like to get suggestion how to troubleshoot this, as this is totally > against > what I read, that Cassandra is scaled linearly. > > > >
