As Jake suggested, you could firstly increase "compaction_throughput_mb_per_sec" and "concurrent_compactions" to suitable values if system resource is allowed. From my understanding, major compaction will internally acquire lock before running compaction. In your case, there might be a major compaction blocking the pending following compaction tasks. You could check the result of "nodetool compactionstats" and C* system log for double confirm.
If the running compaction is compacting wide row for a long time, you could try to tune "in_memory_compaction_limit_in_mb" value. Thanks, On Sun, Jun 8, 2014 at 11:27 PM, S C <as...@outlook.com> wrote: > I am using Cassandra 1.1 (sorry bit old) and I am seeing high pending > compaction count. "pending tasks: 67" while active compaction tasks are > not more than 5. I have a 24CPU machine. Shouldn't I be seeing more > compactions? Is this a pattern of high writes and compactions backing up? > How can I improve this? Here are my thoughts. > > > 1. Increase memtable_total_space_in_mb > 2. Increase compaction_throughput_mb_per_sec > 3. Increase concurrent_compactions > > > Sorry if this was discussed already. Any pointers is much appreciated. > > Thanks, > Kumar >
