Device reservation management for overcoming communication path disruptions

An apparatus for a host in a data storage system comprising a host and a primary data storage system having a primary storage controller and a primary device controlled by the primary storage controller and configured to store data, and at least one secondary data storage system having a secondary storage controller and a secondary device controlled by the secondary storage controller and configured to store data, comprising:

• input/output (I/O) request logic of a host, configured to issue I/O data requests to a primary device which is in a synchronous mirroring relationship with at least one secondary device, wherein the primary device is reserved for exclusive use by the host for I/O data requests, wherein the reservation of the primary device is extended to the at least one secondary device of the mirroring relationship;
• primary-secondary role swap logic of the host configured to manage the primary and secondary devices of the mirroring relationship for selective swapping of primary and secondary roles of the primary and secondary devices, respectively;
• and
• device reservation management logic of the host configured to, in response to a loss of communication connectivity on all communication paths from the host to the primary storage controller controlling the reserved primary device and in response to reestablishment of at least one communication path from the host to the primary storage controller controlling the reserved primary device, confirm whether the primary device remains reserved for exclusive use by the host for I/O data requests;
• and
• wherein the I/O request logic is further configured to, upon successful confirmation that the primary device remains reserved to the host, issue an I/O data request to the primary device instead of issuing the I/O data request to a secondary device of the mirroring relationship.

A method, comprising:

• issuing by input/output (I/O) request logic of a host, I/O data requests to a primary device which is in a synchronous mirroring relationship with at least one secondary device wherein the primary device is reserved for exclusive use by the host for I/O data requests, wherein the reservation of the primary device is extended to the at least one secondary device of the mirroring relationship and the primary and secondary devices of the mirroring relationship are managed by primary-secondary role swap logic of the host to provide for selective swapping of primary and secondary roles of the primary and secondary devices, respectively;
• in response to a loss of communication connectivity on all communication paths from the host to the primary storage controller controlling the reserved primary device and reestablishment of at least one communication path from the host to the primary storage controller controlling the reserved primary device, confirming by device reservation management logic of the host whether the primary device remains reserved for exclusive use by the host for I/O data requests;
• and
• upon successful confirmation that the primary device remains reserved to the host, issuing by the I/O request logic of the host, an I/O data request to the primary device instead of issuing the I/O data request to a secondary device of the mirroring relationship.