When running backup scripts etc. I'm generally tuning them using nice & ionice to tune down the priority of my backup scripts to avoid affecting the mysqld performance.
However, I've been thinking that it would make sense to go the other way around and tune up the io priority and niceness of the mysqld server.
From what i've read either a ionice level in the "real time" class or a really low niceness would make sense. The low niceness would help since default ionice level seems to be "best-effort" with highest priority and the internal priority in the best-effort class is based on process niceness.
I'm a bit worried that the real time class could starve other system level tasks. However - the same could be said for a low niceness. Have anyone experimented with this and what are your findings?
We're running a dedicated mysql server (only other process we 'care' about it sshd) on mechanical hard drives.