Installation guide

10 Chapter 2. Hardware Installation and Operating System Configuration
Performance requirements of applications and users
Choose a hardware configuration that provides adequate memory, CPU, and I/O re-
sources. Be sure that the configuration chosen can handle any future increases in
workload as well.
Cost restrictions
The hardware configuration chosen must meet budget requirements. For example,
systems with multiple I/O ports usually cost more than low-end systems with fewer
expansion capabilities.
Availability requirements
In a mission-critical production environment, a cluster hardware configuration must
protect against all single points of failure, including: disk, storage interconnect, Eth-
ernet channel, and power failure. Environments that can tolerate an interruption in
availability (such as development environments) may not require as much protection.
Data integrity under all failure conditions requirement
Using fence devices in a cluster configuration ensures that service data is protected
under every failure condition. These devices enable a node to power cycle another
node before restarting its services during failover. Power switches protect against data
corruption in cases where an unresponsive (or hung) node tries to write data to the
disk after its replacement node has taken over its services.
If you are not using power switches in the cluster, cluster service failures can result
in services being run on more than one node, which can cause data corruption. Refer
to Section 2.5.2 Configuring a Fence Device for more information about the benefits
of using power switches in a cluster. It is required that production environments use
power switches in the cluster hardware configuration.
2.1.1. Minimum Hardware Requirements
A minimum hardware configuration includes only the hardware components that are re-
quired for cluster operation, as follows:
• At least two servers to run cluster services
• Ethernet connection for sending heartbeat pings and for client network access
• Network switch or hub to connect cluster nodes and resources
• A fence device
The hardware components described in Table 2-1 can be used to set up a minimum cluster
configuration. This configuration does not ensure data integrity under all failure conditions,
because it does not include power switches. Note that this is a sample configuration; it is
possible to set up a minimum configuration using other hardware.