Server
Reserved for other services (MB)
PHP-FPM ≈ pm.max_children × worker size. Dedicated mode sets every service except the OS to 0.
Connections
Recommended buffer pool
1920 MB
innodb_buffer_pool_size
innodb_buffer_pool_size
innodb_buffer_pool_instances
Rounding unit (chunk × instances)
Share of total RAM
innodb_dedicated_server would set
Formula
pool = min((RAM − reserved − max_connections × per_conn) × 0.9, RAM × 0.8)
→ round down to a multiple of 128 MB × instances
Memory breakdown
InnoDB buffer pool
Connections
Reserved (OS + PHP-FPM + Redis + web + other)
Total
Left for MySQL global buffers and page cache
my.cnf snippet
Reverse: RAM needed to cache your InnoDB data
Uses the same reservations and connections as above. Add room for growth.
Measure your InnoDB data size (run in the mysql / mariadb client)
SELECT ROUND(SUM(data_length + index_length) / 1024 / 1024 / 1024, 2) AS innodb_gb FROM information_schema.tables WHERE engine = 'InnoDB';