DateTieredCompactionStrategy (DTCS) was introduced in Cassandra 2.0.11. It was designed specifically for time series work loads that do append-only writes, exactly as we do with the data table. Used in conjunction with a default TTL on the table, DTCS can reduce disk I/O and CPU usage during compaction.
There is another big benefit of using a default TTL on the data table - reduced disk usage. We no longer include a TTL with each write, which is a savings of 4 bytes per cell. This could be a substantial savings for environments like OpenShift that have high ingestion rates and are potentially dealing with large amounts of metric data.