Reclaiming disk space in MySQL 8 can be a critical task, especially when dealing with large databases or systems with limited storage. Disk space can be consumed by a variety of factors, including data growth, fragmentation, and logs. Here are key methods to reclaim disk space in MySQL 8:

1. Optimize Tables

• Usage: The OPTIMIZE TABLE command can be used to defragment tables, which can free up space. It's particularly effective after a large number of deletions or updates.

  OPTIMIZE TABLE your_table_name;
  
  

• Consideration: This operation can be resource-intensive and might lock the table during the process.

2. Drop Unused Indexes and Tables

• Unused Indexes: Dropping unused or redundant indexes can free up a significant amount of space.
• Unused Tables: If there are any tables that are no longer needed, consider dropping them.

3. Purge Binary Logs

• Binary Logs: If you have binary logging enabled, old binary logs can take up a lot of space.

• Purge Command: Use PURGE BINARY LOGS to delete old logs.

  PURGE BINARY LOGS BEFORE 'YYYY-MM-DD hh:mm:ss';
  
  

• Automate Purging: Set the expire_logs_days system variable to automatically purge old binary logs.

4. Archiving Old Data

• Data Archiving: Move old or rarely accessed data to a different database or storage medium.
• Partitioning: For large tables, consider partitioning, where older partitions can be dropped or archived.

5. Reduce the Size of the InnoDB Log File

• InnoDB Log File: If the InnoDB log file (iblogfile) is too large, consider resizing it.
• Caution: This requires careful planning as it involves changing configuration (innodb_log_file_size) and restarting MySQL, which will recreate the log files.

6. Clean Up the InnoDB Temporary Tablespace

• InnoDB Temp Tablespace: The InnoDB temporary tablespace (ibtmp1) can grow over time. Restarting MySQL will reset its size.
• Regular Monitoring: Keep an eye on the size of ibtmp1 to prevent it from consuming excessive disk space.

7. Use Data Compression

• Table Compression: For InnoDB, use ROW_FORMAT=COMPRESSED to compress table data. This feature is available in MySQL 5.7 and 8.0 but deprecated in MySQL 8.0.20 and later.
• Filesystem Compression: Consider using a filesystem that supports compression.

8. Delete or Archive Slow Query Logs and General Logs

• Log Files: If general query logs and slow query logs are enabled, they can grow over time. Regularly delete or archive these logs.

9. Check for Unused Schema Objects

• Schema Cleanup: Look for and remove any unused databases, stored procedures, views, or other schema objects that may be occupying space.

Conclusion

Reclaiming disk space in MySQL involves a combination of table optimization, log management, archiving old data, and cleaning up unnecessary database objects. It's important to regularly monitor disk usage and perform these maintenance tasks as part of routine database administration. Always ensure to back up your data before performing operations that might affect your data or database structure.