Specifications

Planning Your SPS Environment
The following topics will assist in defining the SPS for Linux cluster environment.
Mapping Server Configurations
Document your server configuration using the following guidelines:
1. Determine the server names, processor types, memory and other I/O devices for your
configuration. When you specify a backup server, you should ensure that the server you select
has the capacity to perform the processing should a failure occur on the primary server.
2. Determine your communications connection requirements.
Important: Potentially, clustered configurations have two types of communications
requirements: cluster requirements and user requirements.
l Cluster - A LifeKeeper cluster requires at least two communication paths (also called “comm
paths” or “heartbeats”) between servers. This redundancy helps avoid “split-brain” scenarios
due to communication failures. Two separate LAN-based (TCP) comm paths using dual
independent subnets are recommended, and at least one of these should be configured as a
private network. Using a combination of TCP and TTY is also supported. A TTY comm path
uses an RS-232 null-modem connection between the servers’ serial ports.
Note that using only one comm path can potentially compromise the ability of systems
in a LifeKeeper cluster to communicate with each other. If a single comm path is used
and the comm path fails, then LifeKeeper hierarchies may try to come into service on
multiple systems simultaneously. This is known as a false failover or a “split-brain”
scenario. In the “split-brain” scenario, each server believes it is in control of the
application and thus may try to access and write data to the shared storage device. To
resolve the split-brain scenario, LifeKeeper may cause servers to be powered off or
rebooted or leave hierarchies out-of-service to assure data integrity on all shared data.
Additionally, heavy network traffic on a TCP comm path can result in unexpected
behavior, including false failovers and the failure of LifeKeeper to initialize properly.
l User - We recommend that you provide alternate LAN connections for user traffic - that is, a
separate LAN connection than the one used for the cluster heartbeat. However, if two TCP
comm paths are configured (as recommended), one of those comm paths can share the
network address with other incoming and outgoing traffic to the server.
l Note: To help ensure that resources are brought into service only when necessary, you may
elect to utilize the Quorum/Witness Server Support Package for LifeKeeper.
3. Identify and understand your shared resource access requirements. Clusters that use shared
storage can utilize either shared SCSI buses or Fibre Channel loops. Because LifeKeeper
locks resources to one server, you must ensure that only one server requires access to all
SteelEye Protection Suite for Linux7