HP Serviceguard Extended Distance Cluster for Linux A.11.20.10 Deployment Guide, December 2012

3 Configuring your Environment for Software RAID
The previous chapters discussed conceptual information on disaster recovery architectures and
procedural information on creating an extended distance cluster. This chapter discusses the
procedures you need to follow to configure Software RAID in your extended distance cluster.
3.1 Understanding Software RAID
Redundant Array of Independent Disks (RAID) is a mechanism that provides storage fault tolerance
and, occasionally, better performance. Software RAID is designed on the concept of RAID 1. RAID
1 uses mirroring where data is written to two disks at the same time.
The serviceguard-xdc product uses the Multiple Device (MD) driver and its associated tool mdadm
to implement Software RAID. With Software RAID, two disks (or disk sets) are configured so that
the same data is written on both disks as one "write transaction". So if data from one disk set is
lost, or if one disk set is rendered unavailable, the data is always available from the second disk
set. As a result, high availability of data is guaranteed. In an extended distance cluster, the two
disk sets are in two physically separated locations, so if one location becomes unavailable, the
other location still has the data.
For more information on Linux Software RAID, see The Software-RAID HOWTO manual available
at http://www.tldp.org/HOWTO/Software-RAID-HOWTO.html.
To enable Software RAID in your extended distance cluster, you need to complete the following:
1. Install the extended distance cluster software.
2. Configure packages that will use Software RAID.
3.2 Installing the Extended Distance Cluster Software
This section discusses the supported operating systems, prerequisites and the procedures for installing
the Extended Distance Cluster software.
3.2.1 Supported Operating Systems
The serviceguard-xdc version A.11.20.10 supports the following operating systems:
• Red Hat Enterprise Linux 5 or later
• Red Hat Enterprise Linux 6 or later
• SUSE Linux Enterprise Server 11
For information about supported configuration, see HP Serviceguard for Linux Certification Matrix
at www.hp.com/go/linux-serviceguard-docs.
3.2.2 Prerequisites
Following are the prerequisites for installing serviceguard-xdc version A.11.20.10:
• HP Serviceguard for Linux A.11.20.10
serviceguard-xdc version A.11.20.10 works with only HP Serviceguard A.11.20.10.
• Ensure that mdadm and udev rpms are installed on your system.
• Network Time Protocol (NTP) - all nodes in the cluster to point to the same NTP server.
3.2.3 Installing serviceguard-xdc Software
First time installation
If you are installing the serviceguard-xdc software for the first time:
3.1 Understanding Software RAID 19