We went on the hunt for a time-series data-store a while ago and ended up picking OpenTSDB. It seems they are planning on supporting Cassandra (which sounds like it will be easier to maintain than HBase): <a href="http:&#x2F;&#x2F;opentsdb.net&#x2F;docs&#x2F;build&#x2F;html&#x2F;user_guide&#x2F;backends&#x2F;cassandra.html" rel="nofollow">http:&#x2F;&#x2F;opentsdb.net&#x2F;docs&#x2F;build&#x2F;html&#x2F;user_guide&#x2F;backends&#x2F;cass...</a> 
Another worthy contender was KairosDB: <a href="https:&#x2F;&#x2F;kairosdb.github.io&#x2F;" rel="nofollow">https:&#x2F;&#x2F;kairosdb.github.io&#x2F;</a>