3.1.2 Matrix Server Administration Guide

Chapter 1: Introduction 11

• An HTTP service monitor is configured on each server. If this monitor

detects that the HTTP service has failed, the associated virtual host

will fail over to a backup server where the HTTP service is healthy.

The client requests will then be processed on that server.

•Two

SHARED_FILESYSTEM device monitors are configured on each

server for the PSFS filesystems (/www and /httpd-logs). These monitors

check the mount status and health of the mounted PSFS filesystems.

The four virtual hosts are also associated with each monitor. If a

monitor detects a problem with a filesystem, any active virtual hosts

associated with the monitor will fail over to a backup server where the

filesystem mount is healthy. The client requests will then be processed

on that server.

Support for Administrative Tasks

Because the Web site data and access logs are on shared PSFS filesystems,

they can be accessed from any server in the matrix. A server failure does

not prevent the administrator from accessing log files or updating the

Web site data.

The sample configuration includes two virtual hosts that are used to run

custom scripts that process log file data or perform the updates. The use

of virtual hosts ensures that the administrator will always reach an “up”

server when it is necessary to perform administrative tasks.

Matrix Design Guidelines

Be sure to consider the following guidelines when planning the physical

configuration of your Matrix Server matrix.

Server Memory

Memory resources are consumed on each matrix server to manage the

state necessary to preserve the coherency of shared filesystems. For this

reason, the servers in the matrix should have approximately equal

amounts of physical memory. As a guideline, the ratio of memory

between the smallest and largest servers should not exceed 2. For

example, the smallest server could have 1 GB of memory and the largest

server 2 GB. If this ratio is exceeded (such as a 256 MB server and a 2 GB