Techniques manage a storage system. Such techniques involve: determining an expected input/output (I/O) concurrency number of an access request for a storage system, the access request being associated with a first one of a plurality of redundant arrays of independent disks (RAIDs) comprised in the storage system; in response to a current available I/O concurrency number of the first RAID being less than the expected I/O concurrency number, increasing the available I/O concurrency number of the first RAID based on a reserved I/O concurrency number of the storage system; and performing the access request using the first RAID having the increased available I/O concurrency number.