About global-active device

Global-active device (GAD) enables you to create and maintain synchronous, remote copies of data volumes on the Hitachi Virtual Storage Platform G1000 and Virtual Storage Platform G200, G400, G600, G800 storage systems. A virtual storage machine is configured in the primary and secondary storage systems using the actual information of the primary storage system, and the global-active device primary and secondary volumes are assigned the same virtual LDEV number in the virtual storage machine. This enables the host to see the pair volumes as a single volume on a single storage system, and both volumes receive the same data from the host.

A quorum disk located in a third and external storage system is used to monitor the GAD pair volumes. The quorum disk acts as a heartbeat for the GAD pair, with both storage systems accessing the quorum disk to check on each other. A communication failure between systems results in a series of checks with the quorum disk to identify the problem for the system able to receive host updates.

Alternate path software on the host runs in the Active/Active configuration. While this configuration works well at campus distances, at metro distances Hitachi Dynamic Link Manager (HDLM) is required to support preferred/nonpreferred paths and ensure that the shortest path is used.

If the host cannot access the primary volume (P-VOL) or secondary volume (S-VOL), host I/O is redirected by the alternate path software to the appropriate volume without any impact to the host applications.

Global-active device provides the following benefits: