Storage and Disk Usage Analysis

Diagnose disk usage, compression efficiency, part sizes, and storage bottlenecks.

Diagnostics

Run all queries from the file checks.sql and analyze the results.

Ad-Hoc Query Guidelines

Required Safeguards

-- Always limit results limit 100

-- For part_log where event_date >= today() - 1

Key Tables

• system.disks

• Disk configuration

• system.parts

• Part storage details

• system.columns

• Column compression

• system.storage_policies

• Tiered storage

• system.detached_parts

• Orphaned parts

Cross-Module Triggers

Finding Load Module Reason

Poor compression altinity-expert-clickhouse-schema

Codec recommendations

Many small parts altinity-expert-clickhouse-merges

Merge backlog

High write IO altinity-expert-clickhouse-ingestion

Batch sizing

System logs large altinity-expert-clickhouse-logs

TTL configuration

Slow disk + merges altinity-expert-clickhouse-merges

Merge optimization

Settings Reference

Setting Notes

min_bytes_for_wide_part

Threshold for Wide vs Compact parts

min_rows_for_wide_part

Row threshold for Wide parts

max_bytes_to_merge_at_max_space_in_pool

Max merge size

prefer_not_to_merge

Disable merges (emergency)