MySQL MyISAM Key Cache Hit Rate and Cache Hit Rate Warning

[nagios-retail]

Hello,

We have setup a new Nagios server and added tests from an older Nagios environment.
2 of these test are:
MySQL MyISAM Key Cache Hit Rate
MySQL Query Cache Hit Rate

They both return a critical warning:
CRITICAL - myisam keycache hitrate at 89.81%
CRITICAL - query cache hitrate 38.66%

Since these test come with a Nagios wizard: " check_xi_mysql_health " I dont want to change the values of the tests.
How can i get these tests to work properly and what exactly do they monitor?
The Nagios that is running them only has 19 hosts and 244 services running so it can't be a performance problem.

[benjaminsmith]

Hi,

If you're getting too many notifications, I think it's fine to adjust your thresholds, at least temporarily. Below are a few pages from the MySQL documentation that describes these metrics.

The MyISAM Key Cache

The MySQL Query Cache

Basically, these two metrics are measure how much database activity is coming from the cache ( a good thing). You can adjust your MySQL configuration to increase the memory and buffer size to improve these metrics (assuming you have enough memory).

Hope that helps clarify these metics and let us know if you have any other questions.

--Benjamin