Figure 1 - Replication Setup

Also, the figure shows at a high level how the data replication is connected. In the primary cluster, the primary replication group has two devices: a source device (connected to the primary site labeled as device A) and a destination (connected to the secondary site and labeled as device B). Data is replicated via storage data replication facilities (e.g. Continuous Access) continuously from source to destination. On the secondary site, a local mirror is associated with the destination devices (labeled as device B’). The mirror technology is storage specific (e.g. Business Copy). This local mirror also acts as a source device for the recovery replication group and recovery during rolling disasters. In the recovery cluster, the destination device (labeled as device C) of the recovery replication group are connected to the nodes in the cluster. Data is periodically replicated to the destination devices via storage data replication technology. Also, a local mirror of the destination device is required for cases of rolling disasters (labeled as device C’).

Currently, HP StorageWorks XP Continuous Access (CA) and EMC Symmetrix SRDF technologies are supported for the multi-site disaster tolerant solution.

Purpose

This document introduces the cascaded configuration in a Continentalclusters environment. This includes configuration, maintenance, and recovery procedure for the cascaded configuration environment.

Terminology

Throughout this document, the following terms refer to high level operations performed under a cascaded configuration scenario. These defined terms are not general terms that are used in other documents referring to data replication, clustering, and multi-site disaster tolerant solutions.

The device where I/O can be performed is referred to as the source. The data that is written to the source device will be replicated to another device remotely. This remote device is referred to as the destination (or destination device). For the XP CA data replication technology, the correct terminology for source and destination are PVOL and SVOL respectively. For the EMC SRDF data replication technology, source and destination are R1 and R2 respectively. Local mirror is the name for a local copy of a device on the same disk array. Business Copy (BC) for HP XP and Business Continuance Volumes (BCV) for EMC SRDF are the supported local mirroring capabilities used for the Metrocluster and Continentalclusters products. A replication group is a pairing of source and destination devices where the source replicates data to its assigned destination. In the cascaded configuration, there are two replication groups. The replication group in the primary cluster is referred to as the primary

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