What is the requirement to configure I/O fencing on Virtual Machines.

Problem

Virtual Machines were added to an existing cluster with physical nodes. When vxfen was started it failed.

Error Message

vxfen log showed following errors.

Tue Jan 11 20:30:32 GMT+8 2011 output was VXFEN vxfenconfig ERROR V-11-2-1006 List of coordinator disks in running

 cluster is different than local node.

 Unable to configure vxfen

Log Buffer: 0xffffffff889b5f40

VXFEN vxfenconfig NOTICE Driver will use SCSI-3 compliant disks.

Tue Jan 11 20:30:32 GMT+8 2011 exiting with 1

Cause

Virtual machine and IO fencing should be configured in a particular way.

Solution

IO fencing and Virtual Machines should be configured as below;

SCSI-3 Persistent reservations are only supported with raw device mapping (RDM) in physical mode. I/O fencing is not supported with RDM logical mode or with VMDK-based virtual disks. I/O fencing utilizes HBA World Wide Numbers (WWNs) to create registrations on the storage; this has implications in a virtual environment where the HBA is shared between virtual servers on the same physical ESX host as the WWN used for I/O fencing ends up being the same for each virtual machine. CFS virtual machines (in the same CFS cluster) cannot share physical servers as the I/O fencing behavior will result in all nodes from that physical ESX host being fenced out if an event triggers the fencing functionality. In short, if I/O fencing is configured, the CFS nodes (in the same CFS cluster) has to be running on separate physical ESX hosts. NPIV is currently under evaluation for I/O fencing testing when using multiple Virtual Machines on the same physical ESX host.

Applies To

Suse 10

vcs 5.1