> Sorry for the delayed reply, but thanks very much - this pointed me at the > exact problem. I found that the queue size here was equal to the number of > configured DataFileDirectories, so a good test was to lie to Cassandra and > claim that there were more DataFileDirectories than I needed. Interestingly, > it still only ever wrote to the first configured DataFileDirectory, but it > certainly eliminated the problem, which I think means that for my use case > at least, it will be good enough to patch Cassandra to introduce more > control of the queue size.
Based on your use case as you originally stated it (some cf:s that got written at a slow pace and just happened to flush at the same time), that should be enough. (If you have some CF:s being written to faster than they are flushed, there would still be potential for one CF to hog the flush writers unfairly.) -- / Peter Schuller
