MySQL 5.7 Release Notes
As a DBA, you must manage disk I/O to keep the I/O subsystem from
becoming saturated, and manage disk space to avoid filling up
storage devices. The ACID design
model requires a certain amount of I/O that might seem redundant,
but helps to ensure data reliability. Within these constraints,
InnoDB tries to optimize the database work and
the organization of disk files to minimize the amount of disk I/O.
Sometimes, I/O is postponed until the database is not busy, or until
everything needs to be brought to a consistent state, such as during
a database restart after a fast
shutdown.
This section discusses the main considerations for I/O and disk
space with the default kind of MySQL tables (also known as
InnoDB tables):
Controlling the amount of background I/O used to improve query performance.
Enabling or disabling features that provide extra durability at the expense of additional I/O.
Organizing tables into many small files, a few larger files, or a combination of both.
Balancing the size of redo log files against the I/O activity that occurs when the log files become full.
How to reorganize a table for optimal query performance.