Storage and Disk Usage Analysis

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

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Diagnostics

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

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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

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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

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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)