Compression Ratio Degradation

info

cost_managementUpdated Jan 7, 2026

Declining compression ratios indicate data characteristics changing or suboptimal codec settings, increasing storage costs and I/O overhead.

Sources

Useful queries for troubleshooting | ClickHouse Docsclickhouse.com

How to engineer cost-efficient open source observability with ClickHouse (ClickStack) - 2026 technical playbookclickhouse.com

Technologies:

ClickHouseSymptoms of this issue are visible in ClickHouse metrics and logs

clickhouse.columns.compressed_size

clickhouse.columns.uncompressed_size

clickhouse.columns.compression_ratio

How to detect:

Track data_compressed_bytes/data_uncompressed_bytes ratio from system.columns over time. Alert when compression ratio degrades significantly (e.g., drops below 5:1 for typical analytical data).

Recommended action:

Review and optimize codec settings per column type (e.g., Delta for timestamps, LZ4 for general data, ZSTD for maximum compression), implement codec chaining for better compression, or investigate data quality issues causing low compressibility.