I'm thinking about implementing a trigger to create a log table for one of my innodb tables. Does anyone know of any performance issues that would be caused by using a trigger for this, outside the fact that mysql will need to do an insert everytime the trigger is fired?

Thank you,

A trigger is a special type of stored procedure. Calling a trigger is a very small performance hit, but obviously the code inside the trigger can slow things down. But that insert will take far longer than having the server implicitly call the trigger.