StatsDawg

These statistics are specific to the performance of the MyISAM storage engine. MyISAM is the default storage engine in MySQL but can require some tunining in order to get the best performance benefit from it. Though more items will be added in the future, for now this section provides information about the key buffer. The key buffer is used to store indexes in RAM for fast access and should generally be allocated a generous portion of RAM to do so.

The Key Buffer Used stat show the amount of used RAM, both in megabytes, and as a percentage, for the key buffer. If this value is low compared to the amount of RAM allocated to the key buffer, you may want to decrease the amount of RAM for this purpose so that it can be use elsewhere. By contrast, if it very close to the max, it may indicate that you want to increase the amount of RAM devoted to the key buffer.

The Key Buffer Hit Rate is the percentage of 'hits' to the buffer. In other words, this shows the percentage of time that an index MySQL needed to reference was already in the buffer. A low hit rate can indicate that the buffer may not be big enough or is simply not being well utilized. A high hit rate, of course, indicates that the key buffer is being utilizied very well.