For background see the JVM Heap Size section here http://wiki.apache.org/cassandra/MemtableThresholds
You can also add a fudge factor of anywhere from X2 to X8 to the size of the memtables. You are in for a very difficult time trying to run cassandra with under 500MB of heap space. Is this just a test or are you hoping to run it in production like this ? If you need a small single instance schema free data store would redis suit your needs ? Hope that helps. Aaron On 2 Apr 2011, at 01:34, openvictor Open wrote: > Hello everybody, > > I am quite new to Cassandra and I am worried about an apache cassandra server > that is running on an small isolated server with only 2 Gb of RAM. On this > server there is very little data in Cassandra ( ~3 Mb only text in column > values) but there are other servers such as : SolR, Tomcat, Redis, > PostGreSQL. There is quite a lot of column families (about 15) but some > column families are empty at the moment. At the moment memory consumption is > 484 Mb real and 948556 in virtual. > > I modified the storage-conf ( I am running apache cassandra 0.6.11) I set > DiskAccessMode in standard since I am running on debian 64 bits. I also set > the MemtableThroughput to 16 Mb instead of 64 Mb and I lower the Xms value to > and Xmx to 128M and 256M. > > My question is : where does this giant memory overhead comes from (484 Mb for > 3 Mb of data seems insane) ? And more importantly : how can I set Cassandra > to use maximum let's say 500 Mb, because at this rate Cassandra will be well > over that limit soon. > For information because of security I cannot use JMX, except if there is a > way to use JMX without an interface through SSH. > > Thank you for your help. > Victor
