InnoDB is likely your storage engine of choice for MySQL as it
provides transactional support, as well as crash protection.
"Typically the InnoDB buffer cache should get the bulk of memory
on the system. So for example if you are just running MySQL on your
server (we hope so), then perhaps 20% of the memory can go to the
OS, 20-30% to sessions, and the remaining 50% to static buffers in
MySQL. If you're not using MyISAM most of that 50% will be for this
InnoDB buffer pool.
calculate innodb buffer pool hit ratio
1 - (innodb_buffer_pool_reads / innodb_buffer_pool_read_requests)
"A hit ratio is not a bulletproof way to tune I/O, but it can
give you a good indication and starting point from which to tune.
Since InnoDB caches both data and index in this buffer pool, the
hit ratio here will tell you overall the % of hits that are
satisfied by going to memory versus the ones which require disk
I/O. You want to do as little disk I/O as possible, so a higher hit
rate here means you're caching better and more relevant blocks to
your applications needs."