I’m puzzled by the behavior of my key cache. The cache read ratio is currently 6.55% which is said to be high, and there are 2.7 million reads out of 46 million read requests. This is over about 6.4 million MySQL requests (last 5 days).
But at the same time there are 32K unused blocks against only 22K used blocks.
The comment against the 2.7 million reads (in red) is “If Key_reads is big, then your key_buffer_size value is probably too small”.
With more free space than used, how would increasing the key buffer size any further help? And with so much free space, why is the performance of the key cache so poor?