A method uses a record of I/O priorities in a determination of a storage medium of a hybrid storage system in which to store a file. The method maintains the record of I/O priorities by assigning an I/O temperature value to each request for access to the file based upon an I/O priority level of the process making the request. The method marks the file as hot if the file temperature value is greater than a threshold value. The method stores files marked as hot in a lower latency storage medium of the hybrid storage medium.