Serviceguard Extended Distance Cluster (EDC) with VxVM/CVM Mirroring on HP-UX, May 2008

Introduction
Management Summary
An Extended Distance Cluster (EDC) is a “special” Serviceguard cluster architecture that protects
against multiple failures, such as a complete datacenter failure, by extending a single Serviceguard
cluster across two datacenters. A key component is the data replication method between the two
datacenters. Since data replication is based on volume manager functionality, an EDC is independent
from the type of shared storage.
Serviceguard supports two volume managers. Most standard Serviceguard documentation includes
references to the configuration with LVM. This document focuses on the VxVM/CVM configurations in
an EDC. It explains the VxVM/CVM features that are important for EDC configurations. The reader
also learns why those features are important for an EDC and how to take advantage of them while
performing administrative tasks. EDC specific failure cases are illustrated, including expected
reactions and the recovery procedures.
Terms and Definitions
Term Definition
CFS Cluster File System—A file system that is available for concurrent read and write access to multiple
nodes, or all nodes, in a cluster.
CVM VERITAS Cluster Volume Manager—Enables multiple cluster nodes to access volumes concurrently.
DCO Data Change Object
DCL Data Change Log
DMP Dynamic Multipathing
DRL Dirty Region Log
DWDM Dense wavelength division multiplexing is a fiber-optic transmission technique that employs light
wavelengths to transmit data.
EBN Enclosure-Based Naming—A VxVM/CVM naming scheme that includes the “enclosure” name as
part of the VxVM disk name
FMR FastMirrorResync—also called FastResync (FR); both terms are used in this document
ISL Inter-Site Link—A link between two sites that carries the cluster heartbeat and storage traffic
plex VxVM naming convention for a mirror
SDH Synchronous Digital Hierarchy — A standard technology for synchronous data transmission on
optical media
SGeRAC HP Serviceguard Extension for Oracle Real Application Clusters (RAC)
SMS HP Serviceguard Storage Management Suite—other abbreviations : HP SMS, HP SG SMS, or
SGSMS
SONET Synchronous Optical NETwork—A physical layer network technology designed for data
transmission over fiber optic cabling
TOC Transfer Of Control—A method to immediately halt the SPU without a graceful shutdown to
preserve data integrity
VxFS VERITAS File System
VxVM VERITAS Volume Manager
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