Computer system, cache control method, and server

A computer system, comprising: a server on which an application providing a service runs; and a storage system for storing data, the server including a cache device in which a server cache for temporarily storing data is set up, and an operating system for controlling the server, the operating system including a cache driver for controlling the server cache, wherein the operating system is configured to hold access information storing a frequency of reading data and a frequency of writing data, and wherein the cache driver is configured to: update the access information in a case where an I/O request; analyze access characteristics of data that is a target for the I/O request based on the access information; and determine whether to store the data that is the target for the I/O request in the server cache.