Controller-based bi-directional remote copy system with storage site failover capability

A method for bi-directional replication of data between two sites connected by two links, each site including a local host computer and a node comprising a pair of array controllers coupled to a local data storage array, the method comprising:

• in the situation when either of said links is operational, and at least one cross-link array controller is in communication with its cross-link partner controller,
• presenting logical units residing on each said local data storage array to each respective said local host computer wherein the logical units are part of a remote copy set contained on each said data storage array;
• in the situation when both links are down, or when neither said pair of array controllers can communicate with its cross-link partner controller,
• notifying each said host that all logical units that are part of remote copy sets are not available;
• wherein, if a site failover occurs,
• causing the logical units for the pair of controllers at both said sites to again be visible locally to each said host;
• and
• logging data to a log unit for each logical unit;
• waiting for a failback of the sites to occur;
• and
• wherein, after said failback occurs,
• initiating a merge operation from each said log unit to a corresponding remote copy set member at the other site;
• and
• repeating the above beginning with presenting said logical units.

A method for bi-directional replication of data between two sites connected by two fibre channel fabric links, each site including a local host computer and a node comprising a pair of array controllers coupled to a local data storage array, the method comprising:

• in the situation when either of said links is operational, and at least one cross-link array controller is in communication with its cross-link partner controller,
• presenting logical units residing on each said local data storage array to each respective said local host computer, wherein the logical units are part of a remote copy set contained on each said data storage array;
• wherein, when both links are down, or when neither said pair of array controllers can communicate with its cross-link partner controller,
• notifying each said host that all logical units that are part of remote copy sets are unavailable;
• and
• causing the logical units for the pair of controllers at both said sites to again be visible locally to each said host after notification of site failover is provided.

A method for simultaneous bi-directional replication of data between two sites connected by at least one link, each site including a local host computer and a local node comprising a pair of array controllers coupled to a local data storage array, the method comprising

• simultaneous bi-directional replication of data between two sites;
• including performing copy operations from each host computer to the node at the opposite side of said at least one link;
• and
• performing data I/O operations from each host computer to the local node.