How to Configure High Availability Feature in XenServer

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High Availability (HA) is a set of automatic features designed manage a XenServer pool resources in the event a XenServer host becomes unreachable. This article describes the requirements for using HA within a XenServer pool, how to configure HA, and how to disable HA.

For more information regarding HA, please refer to the XenServer Administrator's Guide:

• XenServer 6.2 - XenServer 6.2.0 Administrator's Guide
• XenServer 6.1 - XenServer 6.1.0 Administrator's Guide
• XenServer 6.0, 6.0.2 - XenServer 6.0 Administrator's Guide

Requirements

• A minimum of three XenServer hosts in a pool
• XenServer versions 6.2 SP1, 6.2, 6.1, 6.0.2, or 6.0 must be installed and fully patched
  •  XenServer 5.x is End-Of-Life
  •  Enterprise Licenses on all hosts prior. (XenServer 6.2 does not require a license to utilize HA)
• Bonded Networking
• Shared, Multipath Storage
• iSCSI, NFS or Fibre Channel LUN with 356MiB (or greater) to be the Heartbeat Storage Repository (SR)

Note: For NetApp or EqualLogic SRs, manually provision an iSCSI LUN on the array (356 MiB or greater) to be used for the Heartbeat SR.

Instructions

Complete the following procedure to enable and disable HA on your XenServer pool:

1. To enable HA for your XenServer pool (with three or more hosts), select the Pool Name/Resource Icon:
   

2. Right-click the Pool Name/Resource Icon and select High Availability...
   

3. Alternatively, with the Pool Name/Resource Icon highlighted, select the HA tab and select Configure HA…
   

4. The Configure HA dialog box appears. Read the requirements before selecting Next.
   

5. The configuration wizard scans the pool for a Hearbeat SR. If no suitable SR is found, the wizard will exit and one must establish the High Availability Heartbeat Storage Repository (per requirements).
   

6. When an appropriate SR is found, select it and press Next.
   

7. The configuration will present all VMs that are currently in the pool. It is from this configuration dialog will allow one or multiple VMs to be selected as to specify:

   1. The HA restart priority that defines if VMs should be – with enough resources available in the pool – Restarted,Restarted if Possible, and Do Not Restart
   2. The Restart Order - 0 being the highest - that specifies the priority of a VM (or VMs) to be started under a fail-over condition
   3. The Attempt to start next VM delay that specifies how much time should pass before starting the next priority-based VM (or group of VMs).  This is to ensure pool resources are not overwhelmed when recovering from a fail-over condition

1. When the HA conditions are specified, selecting Next presents a review of the HA config. Pressing Finish confirms the configuration and apply it to the pool.
   

2. With the successful application of the HA configuration across the pool, the HA tab should show the following:
   

3. To begin the process of disabling HA for your XenServer pool (with three or more hosts), select the Pool Name/Resource Icon:
   

4. With the Pool Name/Resource icon highlighted, select the HA tab and select Disable HA…
   

5. When prompted to disable HA, select YES.
   
   The HA is disabled across the pool (for each member).