WAL log can take significent disk space. So far there are some config to limit it. but it can go very high.
WAL log size = #tablets * log_segment_size_mb * log segments (1 if there is write ops to this tablet, can go up to log_max_segments_to_retain)
Logs are retained even if there is no write for a while.
We could reduce the WAL log usage by
- reduce min_segments_to_retain to 1 instead of 2, a
- reduce steady state consumption of idle tablets, roll a WAL if it has had no writes for a few minutes and size more than a MB or two so that "idle" tablets have 0 WAL space consumed