Abstract: Techniques process and manage a storage unit access. In accordance with such a technique, a data access request which is from a host system and for a first storage unit in the first storage system is received, wherein the first storage unit is a secondary storage unit; and the data access request is forwarded to a second storage unit in a second storage system associated with the first storage unit via a redirection link from the first storage system to the second storage system, wherein the second storage unit is a primary storage unit. Through such techniques, the host system can be allowed to send a data access request for the secondary storage unit, so that the host system does not need to resend the data access request, thereby reducing delay and interruption caused by such requests.

Abstract: Techniques manage a redundant array of independent disks. In such a technique, an instruction to expand the RAID is received, the RAID being formed by a first group of storage devices and including a first group of RAID extents. A second group of RAID extents created on a second group of storage devices and logical units are created on the second group of RAID extents. In response to receiving an indication for a failure of the creation of the second group of RAID extents or the logical units, a notification is generated for indicating a failure of the expansion of the RAID without triggering a shuffling operation, the shuffling operation causing storage extents in the first and second groups of RAID extents to be distributed in the first and second groups of storage devices.