On 21/12/12 17:56, Yiming Sun wrote:
James, you could experiment with Row cache, with off-heap JNA cache, and see if it helps. My own experience with row cache was not good, and the OS cache seemed to be most useful, but in my case, our data space was big, over 10TB. Your sequential access pattern certainly doesn't play well with LRU, but giving the small data space you have, you may be able to fit the data from one column family entirely into the row cache.
I've done some experimenting today with JNA/row cache. Extra 500Mb of heap, 300Mb row cache, latest JNA, set caching=ALL in the schema for all column families in this keyspace.
Getting average 5% row cache hit rate - no increase in cassandra throughput, and increased disk read I/O, basically because I've sacrificed Linux disk cache for the cassandra row-cache.
Load average was 4 (2cpu boxes) for the duration of the cycle, where it was about 2 before, basically because of the disk I/O I think.
So, I think I'll disable row caching again... James M
