Mysql – Monitoring Redis and thesql server for memory and cpu usage

table_cache is the most useful configuration directive to change. Each time MySQL accesses a table, it loads the table into cache. If you've got a high number of tables, it's faster to have them cached.

Take a look at your server variables by running:

show status;

and have a look for the variable open_tables. If this is the same as your table_cache value, and opened_tables keeps going up, then you need to increase the table_cache value in your configuration file. You'll find a balance by experimenting with these variables during peak times. You want to configure it so that at peak times, there are a low amount of opened_tables even after the server has been up for a long time.

key_buffer_size is also a good variable to experiment with. This variable affects the index buffer size, and making this variable bigger increases MySQL's index handling speed. You can look at the variables with the show variables; command again, and compare key_read_requests to key_reads. Ideally, you want the ratio between these two variables to be as low as possible, and you can do this by increasing the size of the key_buffer_size. If you set this variable higher, you will have less writes and reads directly to and from the disk, which was your main concern.

MySQL uses a lot of memory on purpose-- more memory = less disk access = better performance. the constancy of the usage is likely due to table cache, key cache, and query cache. If you want it to use less, you can tune the parameters in your my.conf file; just beware that it may slow down if you take memory away.

Take a look at http://hackmysql.com/mysqlreport ; you may be able to get some helpful information there about tuning it without performance loss.