hi, Have you checked the load-balancing of your 20 nodes? I have the similar experience that 3 nodes' performance is worse than 2 nodes'. The reason was bad load-balance; after reallocating data, the performance becomes expected.
regards, Cao Jiguang 2010-05-24 casablinca126.com 发件人： 史英杰 发送时间： 2010-05-24 10:42:54 收件人： user@cassandra.apache.org 抄送： 主题： Re: Why Cassandra performs better in 15 nodes than in 20 nodes? Hi,Jonathan I am sorry that there is something wrong with the CL I said last time, I checked the test code agagin. The version we used is 0.6.0-Beta3, and both the write and read CL are ConsistencyLevel.ONE. 2010/5/24 Jonathan Ellis <jbel...@gmail.com> ZERO hasn't been the default CL for a long time. You should upgrade to 0.6.1. (Read NEWS first to see what has changed.) 2010/5/23 史英杰 <shiyingjie1...@gmail.com>: > The replication factor is 3, and the consistency level is default, zero. > > 在 2010年5月24日 上午7:25，Jonathan Shook <jsh...@gmail.com>写道： >> >> It would be helpful to know the replication factor and consistency >> levels of your reads and writes. >> >> >> 2010/5/23 史英杰 <shiyingjie1...@gmail.com>: >> > Thanks for your reply! >> > //Were all of those 20 nodes running real hardware (i.e. NOT VMs)? >> > Yes, there are 20 real servers running in the cluster, and one >> > Casssandra >> > instance runs on each server. >> > //Did your driver application(s) run on "real" hardware and how many >> > threads >> > did you use? >> > The clients run on one server of the 20 servers, I used 10 threads to >> > run >> > the write and read tasks. How many threads can make Cassandra get good >> > throughput? >> > Thanks! >> > 2010/5/23 Mark Robson <mar...@gmail.com> >> >> >> >> On 23 May 2010 13:42, 史英杰 <shiyingjie1...@gmail.com> wrote: >> >>> >> >>> Hi, All >> >>> I am now doing some tests on Cassandra, and I found that both >> >>> writes >> >>> and reads on 15 nodes are faster than that of 20 nodes, how many >> >>> servers >> >>> does one Cassandra system contains during the real applications? >> >>> Thanks a lot ! >> >>> >> >>> >> >>> Yingjie >> >> >> >> I'd ask >> >> Were all of those 20 nodes running real hardware (i.e. NOT VMs)? >> >> and >> >> Did your driver application(s) run on "real" hardware and how many >> >> threads >> >> did you use? >> >> Cassandra can only get good throughput with a lot of client threads, >> >> not >> >> just a few. >> >> Mark >> > > > -- Jonathan Ellis Project Chair, Apache Cassandra co-founder of Riptano, the source for professional Cassandra support http://riptano.com
