Installation guide

Section 2.1:Choosing a Hardware Configuration 15
RAID units. These products require extensive testing to ensure reliable operation, especially if the
shared RAID units are based on parallel SCSI buses. These products typically do not allow for online
repair of a failed system. No host RAID adapters are currently certified with Red Hat Cluster Manager.
Refer to the Red Hat web site at http://www.redhat.com for the most up-to-date supported hardware
matrix.
The use of software RAID, or software Logical Volume Management (LVM), is not supported on
shared storage. This is because these products do not coordinate access from multiple hosts to shared
storage. Software RAID or LVM may be used on non-shared storage on cluster members (for example,
boot and system partitions and other filesysytems which are not associated with any cluster services).
2.1.2 Minimum Hardware Requirements
A minimum hardware configuration includes only the hardware components that are required for
cluster operation, as follows:
• Two servers to run cluster services
• Ethernet connection for a heartbeat channel and client network access
• Shared disk storage for the cluster quorum partitions and service data.
See Section 2.1.5, Example of a Minimum Cluster Configuration for an example of this type of hard-
ware configuration.
The minimum hardware configuration is the most cost-effective cluster configuration; however, it in-
cludes multiple points of failure. For example, if the RAID controller fails, then all cluster services
will be unavailable. When deploying the minimal hardware configuration, software watchdog timers
should be configured as a data integrity provision.
To improve availability, protect against component failure, and guarantee data integrity under all fail-
ure conditions, the minimum configuration can be expanded. Table 2–1, Improving Availability and
Guaranteeing Data Integrity shows how to improve availability and guarantee data integrity:
Table 2–1 Improving Availability and Guaranteeing Data Integrity
Problem Solution
Disk failure Hardware RAID to replicate data across multiple disks.
RAID controller failure Dual RAID controllers to provide redundant access to
disk data.
Heartbeat channel failure Point-to-point Ethernet or serial connection between
the cluster systems.