Global-active device (GAD) is a type of remote synchronous data replication on Hitachi storage systems. UCP Advisor enables you to create global-active device pairs in single server, server cluster, and cross-path system configurations.
- Global-active device (GAD) requires the Advanced Edition license.
- Creating a Physical to VSM Global-active device (GAD) pair type is not supported on VSP One B26 and VSP One B28 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.
You can perform create, split, resync, and delete pair operations from the primary storage system only.
A quorum disk, which can be located in a third and external storage system, is used to monitor the global-active device pair volumes. The quorum disk acts as a heartbeat for the global-active device 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.
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
For more information about global-active device on Hitachi storage systems, see Global-Active Device User Guide (MK-92RD8072).