Can you copy and example of your read and write queries? Are they both degrading in the same way performance wise?
On Mon, Feb 9, 2015 at 8:39 PM, Laing, Michael <michael.la...@nytimes.com> wrote: > 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. >> >> >> >> > -- Dominic Letz Director of R&D Exosite <http://exosite.com>
