Knowledge Base

Storage Port Fan-in Ratio

This is defined as the number of initiators sharing the same Storage Processor Port.

VMware recommends reducing the Fan-in Ratio if you encounter SCSI Reservation Failures.

LUN Type

• Make sure that the Host Mode is set to "0x0C"
• Make sure that the Microcode version on XP 10K and 12K arrays is at least 50-09-78-00/00 then enable Host Mode Option 19. For more information, see VMotion failure of virtual machines located on LUSE LUNs on HP XP 10000 and 12000 (8411304). This applies to Virtual LUNs as well.
• To enable additional logging on the array, enable Host Option Mode 519. This has no effect on ESX host logging.

Queue depth, LUN-to-ESX ratio, LUN-to-VM ratio 

• Reduce the Queue Depth on each Server's HBA connected to that array.
• Reduce the number of ESX hosts sharing a given LUN or set of LUNs on that array.
• Reduce the number of virtual machines per LUN so that the possible number of hosts accessing a given LUN is reduced. For example, if you limit the number of virtual machines per LUN to 4, the highest number of ESX hosts running these virtual machines do not exceed 4 in a DRS/HA cluster. 
  
  Note: This option may result in using more LUNs of smaller sizes. The maximum number of LUNs accessible by a ESX 3.x and ESX 4.0 is 256.

Recommended the Queue Depth setting on the HBA

 Number of hosts sharing a LUN         Queue Depth Value

 8                                                         2

 4                                                         4

 2                                                         8

As fewer hosts share a given LUN, the queue depth setting is higher.

Note: VMware has not received similar reports for HP XP 20000 or XP 24000 and the above does not apply to these models. The HBA Driver’s default Queue Depth should be sufficient.  

Changing the Queue Depth

Run the following commands at the ESX Server Console (or the RCLI for VMware ESXi 3.5).

QLogic HBAs

1. Run the following command to identify the HBA's driver name:
   
   # vmkload_mod -l | grep qla
   
   The output appears similar to:
   
   qla2300_707_vmw
   
   
2. Substitute the <driver_name> parameter below with the name from the above output. Substitute the nn parameter with the Queue depth value calculated above.
   
   # esxcfg-module -s "ql2xmaxqdepth=nn" <driver_name>
   # esxcfg-boot -b
   # reboot

1. Run the following command to identify the HBA's driver name:
   
   # vmkload_mod -l | grep lpfcdd
   
   The output appears similar to:
   
   lpfcdd_7xx
   
   
2. Substitute the <driver_name> parameter below with the name from the above output. Substitute the nn parameter with the Queue depth value calculated above
   
   # esxcfg-module -s “lpfc0_lun_queue_depth=nn” <driver_name>
   
   If you have 2 Emulex HBAs in the server, the command is:
   
   # esxcfg-module -s "lpfc0_lun_queue_depth=nn lpfc1_lun_queue_depth=nn" <driver_name>
   # esxcfg-boot -b
   # reboot