GAD Enhanced for NAS

Server and Cluster Administration Guide for Hitachi NAS Platform

Part Number

The NAS Platform Series 5000 gateway servers in conjunction with the the Hitachi Disaster Recovery Solution (HDRS) software, support the global-active device (GAD) feature that maintains identical read or write copies of data in two locations at the same time. GAD Enhanced for NAS (GEfN) takes advantage of this feature to cluster either 2-node or 4-node “stretched clusters” across two sites, with the virtual SMU (vSMU) ideally located on a 3rd site. This synchronous disaster recovery configuration, also referred to as a stretched cluster, creates a stretched cluster stretched across two sites within 500 km of each other.

A stretched cluster with GAD operates similar to a standard HNAS cluster. There is one cluster name and UUID, and clusterwide locks, management requests, and broadcast requests continue to work as they do in a standard HNAS cluster.

Although the stretched cluster works like a standard 4-node HNAS cluster (including NVRAM mirroring), GAD mirrors the data between the storage arrays. The cluster uses the GAD volume, which is available as read or write on both sites. From the NAS perspective, it looks like shared storage because GAD hides the mirroring between the systems and presents the virtual volumes that are accessible to all cluster nodes. Contact your Hitachi Vantara representative for more information about this special configuration and associated documentation (HDRS User Guide MK-97HDRS003; and additional Field (FE) Implementation and Reference Guides).