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Path Failover on Symmetrix LUNs Is Not Working on ESX Server

Details

I have an ESX Server 3.x or 2.5.x system that uses Emulex HBAs that are connected to a FibreChannel (FC) fabric switch that is in turn connected to an EMC Symmetrix SAN. I try to test automatic failover by either disabling some paths on my LUNs or by physically disconnecting the FC HBA cables, but my server does not failover to alternate paths. Why is failover not working?

Solution

There could be many reasons why failover might not work on Symmetrix LUNs on ESX Server hosts. Some similar problems have been resolved by following these troubleshooting steps:
  1. Check that the director bit settings of the FA ports are accessible and verify that the SC3 bit and the SCP2 bit are enabled. The SCP2 flag is not required for ESX Server 3.x. The Common Serial bit (or the C bit) needs to be enabled. Enabling this bit allows ESX Server hosts to collapse multiple paths of Symmetrix SAN LUNs under a single canonical path. The SC3 and SCP2 bits are particularly needed for proper multipathing and failover functionality.

  2. There are FA port bit settings required for ESX Server hosts. They are documented in VMware's SAN Configuration Guide and the EMC Symmetrix configuration guide for ESX Server hosts (an EMC Powerlink document).

  3. All multipathing policies on Symmetrix LUNs must be set to Fixed.

  4. On some Emulex FC HBAs (for example, LightPulse LPe11002-S), the HBA BIOS is configured to use loop first or arbitrated loop topology by default. You will need to change this to a Fiber or Fabric Point to Point configuration. VMware does not support direct connect and arbitrated loop topologies. You can check the Emulex BIOS configuration during the server boot process or use a software utility from Emulex called lpfcutil. This utility is ESX Server version dependent and may also be HBA model dependent, so make sure you download and use the correct one. This utility can be downloaded from the Emulex site at http://www.emulex.com/vmware/support/index.jsp.

Keywords

Emulex, LightPulse, LPe11002-S, ESX 3.x, Failover, Symmetrix, Multipathing, SCP2, SC3, Common Serial bit, C-bit.

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Actions
  • KB Article: 1000317
  • Updated: Aug 14, 2009
  • Products:
    VMware ESX
  • Product Versions:
    VMware ESX 2.5.x
    VMware ESX 3.0.x