You *may* be seeing this https://issues.apache.org/jira/browse/CASSANDRA-2503
It was implemented in 1.1.0 but perhaps data in the original cluster is more compacted than the new one. Are the increases for all CF's are just a few? Do you have a work load of infrequent writes to rows followed by wide reads ? Cheers ----------------- Aaron Morton Freelance Cassandra Developer New Zealand @aaronmorton http://www.thelastpickle.com On 16/01/2013, at 6:23 AM, Reik Schatz <reik.sch...@gmail.com> wrote: > Hi, we are running a 1.1.6 (datastax) test cluster with 6 nodes. After the > recent 1.2 release we have set up a second cluster - also having 6 nodes > running 1.2 (datastax). > > They are now running in parallel. We noticed an increase in the number of > writes in our monitoring tool (Datadog). The tool is using the write count > statistic of nodetool cfstats. So we ran nodetool cfstats on one node in each > cluster. To get an initial write count. Then we ran it again after 60 sec. It > looks like the 1.2 received about twice the amount of writes. > > The way our application is designed is that the writes are idempotent, so we > don't see a size increase. Were there any changes in between 1.1.6 > 1.2 that > could explain this behavior? > > I know that 1.2 has the concept of virtual nodes, to spread out the data more > evenly. So if the "write count" value was actually the sum of all writes to > all nodes in the, this increase would make sense. > > Reik > > ps. the clusters are not 100% identical. i.e. since bloom filters are now > off-heap, we changed settings for heap size and memtables. Cluster 1.1.6: > heap 8G, memtables 1/3 of heap. Cluster 1.2.0: heap 4G, memtables 2G. Not > sure it can have an impact on the problem.
