Building Disaster Recovery Serviceguard Solutions Using Metrocluster with Continuous Access EVA P6000 for Linux B.12.00.00

1 Introduction
This document describes how to configure data replication solutions using HP P6000/EVA disk
Arrays to provide disaster recovery for Serviceguard clusters over long distances. It also gives an
overview of the HP P6000 Continuous Access software and the additional files that integrate HP
P6000/EVA disk Arrays with Metrocluster.
Overview of P6000/EVA and HP P6000 Continuous Access Concepts
HP P6000 Continuous Access provides remote data replication from primary HP P6000/EVA
storage systems to remote HP P6000/EVA storage systems. HP P6000 Continuous Access uses
the remote-copy function of the Hierarchical Storage Virtualization (HSV) controller running the
controller software (VCS or XCS) to achieve host-independent remote data replication.
Remote replication is the continuous copying of data from selected virtual disks on a source (local)
array to related virtual disks on a destination (remote) array. Virtual disks (Vdisks) are user defined
storage allotments of virtual or logical data storage. Applications continue to run while data is
replicated in the background. Remote replication requires a fabric connection between the source
and destination arrays and a logical grouping between source virtual disks and destination virtual
disks.
This section describes some basic remote replication concepts. The topics discussed are:
• Copy Sets
• Data Replication Groups (DR Groups)
• Write modes
• DR group write history log
• Failover
• Failsafe mode
• Failsafe on Link-down/Power-up
Copy sets
A pairing relationship can be created to automatically replicate a logical disk from the source
array to another logical disk in the destination array. A pair of source and destination virtual disks
that have replication relationship is called a copy set. A Vdisk does not have to be part of a copy
set. Vdisks at any site can be set up for local storage and used for activities, such as testing and
backup. Clones and snapclones are examples of Vdisks used in this manner.When a Vdisk is not
part of a copy set, it is not disaster tolerant, but it can use various Vraid types for failure tolerance.
Data replication Groups (DR Groups)
A DR group is a logical group of virtual disks in a remote replication relationship between two
arrays. DR groups operate in a paired relationship, with one DR group being a source and the
other a destination. Hence a DR group can be thought of as a collection of copy sets. The terms
source and destination are sometimes referred to as a DR mode or DR role. Hosts write data to
the virtual disks in the source array, and the array copies the data to the virtual disks in the
destination array. I/O ordering is maintained across the virtual disks in a DR group, ensuring I/O
consistency on the destination array in the event of a failure of the source array. All virtual disks
used for replication must belong to a DR group, and a DR group must contain at least one Vdisk.
When a DR group is first created, a full copy normalization occurs to copy all the data in the DR
group from the source array to the destination array, bringing the source and destination vdisks
into synchronization. Normalizations copy data from the source array to the destination array in
128 KB blocks.
Overview of P6000/EVA and HP P6000 Continuous Access Concepts 5