That is probably because the relevant memtable is flushed to SSTable and the content of the commit log is not required any more so it's rewinding.
See: http://docs.datastax.com/en/cassandra/3.x/cassandra/dml/dmlHowDataWritten.html 2016年12月8日(木) 17:45 Satoshi Hikida <sahik...@gmail.com>: > Hi, > > I have a question about commit log. > > When commit log segment files are remove actually? > > I'm running a single node cluster for a few weeks to test C* performance. > My simple test have been issuing only read and write requests to the > cluster, then the data size (SSTables size) are increasing monotonously. > > Here are customized C* settings in my environment. > - commitlog_total_space_in_mb: 8192 > - memtable_flush_writers: 4 > - memtable_heap_space_in_mb: 2048 > > And here is the node specs used in my environment. > - CPU core: 4 > - Memory: 16GB > - SSD: 100GB * 2 (one for commit log, the other for data) > > In this case, I expected that the total size of the commit log segment > files are increased up to 8GB. However, when the total size is > increased up to 3GB, the commit log segment files are removed and > total size reduced to around 250MB. > > I wonder why commit log segment files are removed before total size is > increased up to 8GB(= commitlog_total_space_in_mb) ? Could anyone give > me some advices? > > > Regards, > Satosh > > > >
