On Wed, Dec 31, 2014 at 11:35 AM, Mikhail Strebkov <streb...@gmail.com>
wrote:
> > How effective are compactions in this CF? "grep %
> /var/log/cassandra/system.log"?
> I'm not sure what type of logs should I share, when I do "grep %
> /var/log/cassandra/system.log" I don't see anything related to this
> long-running compaction. But here is the result of this grep:
>
> INFO [CompactionExecutor:4] 2014-12-30 23:05:45,547
> CompactionTask.java:251 - Compacted 22 sstables to
> [/raid0/cassandra/data/my_keyspace/my_table-6b40d819520d35c1957008d343f23c
> cd/my_keyspace-my_table-ka-15759,]. 131,389,927 bytes to 121,512,669
> (~92% of original) in 65,894ms = 1.758635MB/s. 451,590 total partitions
> merged to 399,267. Partition merge counts were {1:355582, 2:36885, 3:5419,
> 4:1047, 5:267, 6:35, 7:15, 8:14, 9:1, 11:2, }
>
These are the lines I was asking about. The question is how much garbage a
typical compaction removes. It seems in this CF, the answer is "not very
much" so you can expect the result of your major compaction to be about the
same size as input. IOW, it's most like a simple "merge" of the sstables.
=Rob
