Emc Corporation

Jimmy K Seto

Helen S Raizen

Vinay G Rao

Michael E Bappe

Robert J Pellowski

Hitesh Trivedi

Subburaj Ramasamy

A host computer accesses a storage volume via multiple paths and maintains path mode information identifying either an active or standby operating mode. An active-mode path is generally usable, and a standby-mode path is usable under exceptional conditions such as non-availability of an active-mode path. A reason identifier identifies a first operating condition causing the path to be placed in the standby mode. Upon a path-activating event for a standby-mode path, if there is a second operating condition indicating that the path should be maintained in the standby operating mode, then the path is maintained in the standby operating mode and the path mode information is set to identify the second operating condition, and otherwise the operating mode is set to active. A path-activating event can be a manual action by a user or automatic action such as expiration of an aging timer to re-attempt use of a standby path.

Management of path operating mode transitions in multipathing host computer

A host computer accesses a federated storage volume at first and second frames (physical storage assemblies). The host identifies a preferred frame by (1) obtaining representative values of a performance metric for sets of paths to the volume, each set associated with a different frame, and (2) selecting the frame associated with the path set having the best representative value. In one example a response latency is used to detect different distances to the host and identify the closer frame, which will be preferred. Operating modes of the paths for non-preferred frames are set to 'standby'. During subsequent operation using path selection to send storage operations to the volume, the host selects among paths in an 'active' operating mode so as to access the volume at the preferred frame under normal operating condition. Standby paths are reserved for less normal operating conditions, such as when no active path is available.

Identification and use of preferred path groups in host computer based on differential performance

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Wakefield, MA, United States of America

Jimmy K Seto