What to monitor (key indicators) for MySQL server I have installed Munin for monitoring my MySQL database server. It enabled a large amount of MySQL plugins out of the box. Since running these plugins can be CPU expensive I want to limit them to the ones that I actually need, and that is going to tell me something usefull.

Binary/Relay Logs
Command Counters
Connections
Files and tables
InnoDB Buffer Pool
InnoDB Buffer Pool Activity
InnoDB Insert Buffer
InnoDB IO
InnoDB IO Pending
InnoDB Log
InnoDB Row Operations
InnoDB Semaphores
InnoDB Transactions
MyISAM Indexes
Network Traffic
Query Cache
Query Cache Memory
Replication
Select types
Slow Queries
Sorts
Table locks
Temporary objects


So my question is; which of these parameters are key indicators and has any value to monitor?
Without knowing more about your environment and application(s) that your supporting I would suggest starting here:

Innodb Performance Optimization Basics By Peter Zaitsev

This is a great article that will give you a better idea of what metrics you should be paying attention to on the regular.