I'm not a DBA so looking for some advice on tuning a MySQL (MyISAM) database. I've found that during peak hours we are getting pretty severe load spikes which are slowing down the web front-end.
I've also used JMeter to run tests against the server, and with 20 concurrent users, load spikes to 400%. This doesn't seem normal.
I've ran MySQL Tuner and the following have been flagged up:
[!!] Query cache prunes per day: 4351
[!!] Joins performed without indexes: 155460
[!!] Table cache hit rate: 0% (1K open / 11M opened)
The query cache prunes seems straight forward, and I think I could safely increase this to 100MB without any negative scalability isuses.
I'm confused by 'joins without indexes' as all my tables are indexed. Is this more likely to be an issue with queries using non-indexed columns?
The table cache hit rate is also something I'm not sure about. The number of
Open_tables never decreases below 1000, suggesting the tables never close. 1000 is the value of
table_open_cache in my config.