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This test monitors the key buffer cache in the Maria Database server and reports the number of physical reads of a key block, the number of read requests received by the cache and the number of key blocks that have been modified but not flushed to the cache. Using this test, administrators can figure out data mismatch between the cache and the disk and rectify the same before end users start complaining about outdated data from the disk.

Measurement	Description	Measurement Unit	Interpretation
Key_read_requests	Indicates the number of physical reads of a key block from the disk instead of the cache during the last measurement period.	Number	A high value for this measure indicates that the key_buffer_size variable is probably too small to cache the data.
Key_reads	Indicates the number of reads requests received by the cache during the last measurement period.	Number	The higher the count, the better the performance of the server, as it does not need to read the requested key data from disk.
Not_flushed_key_blocks	Indicates the number of key blocks that have been modified in the cache but have not been flushed to the disk during the last measurement period.	Number	A high value for this measure indicates a mismatch of data between the cache and the disk. If the value of this measure increases in a steep manner, then, there may be a mismatch in the data received by the users since the disk may not be updated as son as the data in the cache is modified.