Topologies

High Availability: Single Virtual Service

This topology provides a High Availability service with minimal hardware requirements. See the overview for information on how this setup works.

The documentation that follows assumes that all nodes on the network are set up with correct interfaces and routes for each network they are connected to as per the diagram above.

• Real Servers

  Heartbeat runs on the two Real Servers and handles bringing up the interface for the virtual address. This is the address to which end&nsbp;users should connect and is typically advertised using DNS.

  To configure heartbeat, /etc/ha.d/ha.cf, /etc/ha.d/haresources and /etc/ha.d/authkeys must be installed. The node names in /etc/ha.d/ha.cf and /etc/ha.d/haresources have to be set according to the output of the uname -n command on each real server. The key ultramonkey in /etc/ha.d/authkeys, should be modified to something confidential to the site. The /etc/ha.d/authkeys must be mode 600, this can be done using the chmod command.

  
  chmod 600 /etc/ha.d/authkeys
  
  

  The configuration files supplied expect that the real servers are connected via eth0 and by a null modem connected to /dev/ttyS0. This may be modified but it is highly recommended that heartbeat be run over at least two links as per notes on communication-media failure.

  On Supported versions of Red Hat and Fedora, to ensure that heartbeat starts up on reboot (on run-levels 2, 3, 4 and 5) the chkconfig command is used:

  
  /sbin/chkconfig --level 2345 heartbeat on
  
  

  On Debian, the update-rc.d command is used (note the trailing "."):

  
  /usr/sbin/update-rc.d heartbeat start 2 3 4 5 .
  
  

  To start heartbeat run:

  
  /etc/init.d/heartbeat start
  
  

  After a few moments heartbeat should bring up an IP alias for the virtual address on the first real server that heartbeat is started on, the master. This can be verified using ifconfig. The following output has been truncated show only the eth0:0 interface. Depending on the network configuration of the real server, it is possible that heartbeat will use a different interface.

  
  /sbin/ifconfig
  eth0:0    Link encap:Ethernet  HWaddr 00:90:27:6F:71:67  
            inet addr:192.168.6.240  Bcast:192.168.6.255 Mask:255.255.255.0
            UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
            Interrupt:18 Base address:0x1000 
  
  

  The other server should become the standby and stopping heartbeat on the master with the following command should effect a fail over:

  
  /etc/init.d/heartbeat stop
  
  

  Heartbeat logs debugging and status information to /var/log/messages and this log should be inspected if problems occur. Please see notes on logging to ensure that all logs are written to disk by syslog.

Copyright © 2000-2005, Horms
Last Updated: Tue May 17 17:37:24 2005 +0900

Debian is a registered trademark of Software in the Public Interest, Inc.
Red Hat, the Red Hat Shadowman logo and Fedora are registered trademarks of Red Hat, Inc.
Red Hat may also be refered to as RedHat on this site.
Linux is a registered trademark of Linus Torvalds.
All other trademarks are the property of their respective owners.