While flushing every second increases the number of compactions to be done, the summary disk IO bandwidth usage is still smaller comparing to systems that use WAL, since the data stored in sstables has better compression ratio comparing to data from WAL. See disk usage graphs at https://medium.com/@valyala/high-cardinality-tsdb-benchmarks-victoriametrics-vs-timescaledb-vs-influxdb-13e6ee64dd6b .