Per https://github.com/influxdb/influxdb.com/pull/544#issuecomment-162212071, the https://github.com/influxdb/docs.influxdata.com/blob/master/content/influxdb/v0.9/concepts/storage_engine.md page should be updated with https://github.com/influxdb/influxdb/blob/master/tsdb/engine/tsm1/DESIGN.md.
