How much memory you need depends on a few things such as how many CF's you have, what your data is like, and what the usage patterns are like. There is no exact formula.
Generally… * i would say 4GB of JVM heap is a good start * key and row caches are set when the CF is created, see "help create column family" in cassandra-cli * CF sizes are set using when running create column family, BUT under 0.8 there is a new automagical memory management see http://thelastpickle.com/2011/05/04/How-are-Memtables-measured/ * see the seting in_memory_compaction_limit_in_mb in cassandra.yaml for info on reducing the memory requirements for compaction. The simplest things you can do is increase the JVM heap size to 3 or 4 GB. Cheers ----------------- Aaron Morton Freelance Cassandra Developer @aaronmorton http://www.thelastpickle.com On 26 Jul 2011, at 00:35, lebron james wrote: > >There are many things you can do to lower caches,optimize memtables, and > >tune jvms. > > Please tell what thins i can do to lower caches,optimize memtables, and > tune jvms? > > >From experience with similar-sized data sets, 1.5GB may be too little. > >Recently I bumped our java HEAP limit from 3GB to 4GB to get ?>past an OOM > >doing a major compaction. > > In future i need database more than 10TB, so i need solve problem with ram, > bacause i need use not more that 4 GB ram on 5TB database. >
