Disk Space Management

ClickHouse can store massive amounts of data efficiently thanks to its columnar storage and compression. UptimeDock provides detailed disk space monitoring at the server, database, and table levels, helping you manage storage and plan for growth.

Overview

Disk space monitoring in UptimeDock gives you visibility into:

• Overall disk usage and capacity
• Per-database storage breakdown
• Per-table disk usage with compression statistics
• Parts count for merge optimization insights

Disk Dashboard

The Disk tab provides a quick overview of your ClickHouse server's storage status. Data is refreshed periodically (shown as "X minutes ago received").

Disk Metrics Explained

Databases View

Switch to the Databases tab to see storage breakdown by database. This helps identify which databases consume the most space.

Understanding Database Columns

Use the search box to filter databases by name. Click Show Settings for additional filtering options.

Tables View

The Tables tab shows storage for individual tables, sorted by size. This is essential for identifying which tables consume the most space.

Understanding Table Columns

Common large tables in a typical ClickHouse installation include:

• system.text_log – Server text logs
• system.query_log – Query execution history
• system.part_log – Part merge/mutation history
• system.processors_profile_log – Query processor profiling

-- Set TTL to keep only 30 days of query logs
ALTER TABLE system.query_log
MODIFY TTL event_date + INTERVAL 30 DAY;

-- Check current TTL settings
SELECT database, table, engine, partition_key
FROM system.tables
WHERE database = 'system' AND name LIKE '%log%';

Charts View

The Charts tab provides visual representations of disk usage trends over time. Use this to:

• Identify growth patterns
• Predict when you'll need more storage
• Correlate disk usage with specific events

Setting Up Disk Alerts

Click the Alerts button to configure disk space notifications. You can set alerts at different levels:

Capacity Planning

Use disk monitoring data to plan for future storage needs:

1. Track growth rate – Monitor how much data is added daily/weekly
2. Estimate runway – Calculate how long until you reach capacity
3. Plan ahead – Scale storage before hitting 80% usage

-- Calculate data growth rate
SELECT
    toStartOfDay(event_date) AS day,
    formatReadableSize(sum(bytes_on_disk)) AS daily_size
FROM system.parts
WHERE event_date >= today() - 30
GROUP BY day
ORDER BY day;

-- Estimate days until disk full
SELECT
    formatReadableSize(free_space) AS free,
    formatReadableSize(total_space) AS total,
    round(free_space / (total_space - free_space) * 30, 0) AS days_at_current_rate
FROM system.disks
WHERE name = 'default';

Troubleshooting

Common disk space issues and solutions:

-- Find tables with too many parts (potential merge issues)
SELECT
    database,
    table,
    count() AS parts_count,
    formatReadableSize(sum(bytes_on_disk)) AS size
FROM system.parts
WHERE active = 1
GROUP BY database, table
HAVING parts_count > 100
ORDER BY parts_count DESC;

-- Optimize a specific table (force merge)
OPTIMIZE TABLE database.table_name FINAL;

Best Practices

Recommended TTL settings for system tables:

-- Keep query_log for 14 days
ALTER TABLE system.query_log MODIFY TTL event_date + INTERVAL 14 DAY;

-- Keep text_log for 7 days
ALTER TABLE system.text_log MODIFY TTL event_date + INTERVAL 7 DAY;

-- Keep part_log for 30 days
ALTER TABLE system.part_log MODIFY TTL event_date + INTERVAL 30 DAY;