Sure, other things being equal. Of course, other things are not truly equal and in practice I think dual-quad-core, 32GB servers are at a good sweet spot for a lot of applications.
As a rule of thumb, inserts will be cpu-bound and reads will be ram/io bound. On Mon, Oct 3, 2011 at 11:10 PM, Ramesh Natarajan <rames...@gmail.com> wrote: > Thanks. We are not planning to use row cache because we don't anticipate > requests for the same row coming in often and we would better let the OS do > the caching.. So does this mean in my case instead of running 6 servers > with 100 GB each, I can run 75 servers with 8 GB RAM and set the Xms/Xmx to > 4GB. > thanks > Ramesh > > On Mon, Oct 3, 2011 at 10:25 PM, Jonathan Ellis <jbel...@gmail.com> wrote: >> >> That's misleading, because you don't necessarily need to give the >> memory to the JVM for Cassandra to make use of it. (See, for example, >> >> http://www.datastax.com/dev/blog/whats-new-in-cassandra-1-0-improved-memory-and-disk-space-management.) >> In fact it's counterproductive to increase heap size past the point >> where it can handle the bloom filters + memtables for your data set. >> >> I suspect that the vast majority of deployments will not benefit from >> heaps larger than 4GB, and there is a ticket open to make this the >> default for 1.0: https://issues.apache.org/jira/browse/CASSANDRA-3295 >> >> That said, if you have the choice it's generally better to choose >> more, smaller servers than fewer, larger ones, primarily because it's >> easier to deal with failures. If you had 12 nodes half as expensive, >> for instance, losing one would be 1/12 of your capacity instead of >> 1/6. >> >> On Mon, Oct 3, 2011 at 9:47 PM, Ramesh Natarajan <rames...@gmail.com> >> wrote: >> > I was reading an article >> > @ http://www.acunu.com/products/choosing-cassandra/ >> > and it mentions cassandra cannot benefit from more than 8GB allocated to >> > JVM >> > heap. Is this true? Are these cassandra installations with larger heap >> > sizes? We are planning to have a cluster of 6 nodes with each node >> > running >> > with about 100 GB or so RAM. Will this be a problem? >> > thanks >> > Ramesh >> > >> > from http://www.acunu.com/products/choosing-cassandra/ >> > Memory Ceiling >> > >> > Cassandra typically cannot benefit from more than 8GB of RAM allocated >> > to >> > the Java heap, imposing a hard limit on data size. Taking advantage of >> > big >> > servers with lots of memory or many disks is no problem for Acunu. >> > Thereʼs >> > no memory ceiling for Acunu and as a result, no data ceiling either. >> > Need to >> > use larger servers? Go ahead. >> >> >> >> -- >> Jonathan Ellis >> Project Chair, Apache Cassandra >> co-founder of DataStax, the source for professional Cassandra support >> http://www.datastax.com > > -- Jonathan Ellis Project Chair, Apache Cassandra co-founder of DataStax, the source for professional Cassandra support http://www.datastax.com
