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
(VSP G1000) storage system. A virtual storage machine is configured in the
primary and secondary storage systems using the actual information of the
primary system, and the global-active device primary and secondary volumes
are assigned the same virtual LDEV number in the virtual storage machine.
Because of this, the pair volumes are seen by the host 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:
• Continuous server I/O when a failure prevents access to a data volume
• Server failover and failback without storage impact
• Load balancing through migration of virtual storage machines without
storage impact
1-2
Overview of global-active device
Hitachi Virtual Storage Platform G1000 Global-Active Device User Guide
To Next Page
Loading...
