Operating local caches for a shared storage device

A computer program product comprising a computer readable storage medium having program instructions embodied therewith, the program instructions executable by a processor to cause the computer processor to perform:

• creating a network multicast group in a storage area network (SAN) for a plurality of computer systems that are connected by the SAN, the plurality of computer systems comprising at least three computer systems including a first computer system and a second computer system, the plurality of computer systems each comprising a local cache for a shared storage device;
• prior to one of the first or second computer system writing write data to the shared storage device:
• writing the write data to the local cache of the one of the first or second computer system;
• sending the write data to the plurality of computer systems in the multicast group;
• based on the send operation completing, writing the write data to the shared storage device;
• and
• based on the write operation completing, signaling write completion to an operating system or hypervisor of the first and second computer systems;
• and
• based on one of the first or second computer system requesting a read of read data from the shared storage device:
• waiting for parallel write operations to complete for the read data in the plurality of computer systems in the multicast group;
• retrieving the read data from the local cache of the one of the first or second computer system based on the read data being available in the local cache of the one of the first or second computer system;
• and
• retrieving the read data from the shared storage device and storing the read data in the local cache of the one of the first or second computer system based on the read data not being available in the local cache of the one of the first or second computer system.