Multipath Setting required for VMWare in SAN
A multipath requirement for EMC storage arrays:
All storage arrays Topology: - No single failure should cause both HBA and SP failover, especially with active-passive storage arrays.
EMC Symmetrix : - Enable the SPC2 and SC3 settings.
EMC CLARiiON : - All initiator records must have
- Fail-over Mode = 1
- Initiator Type = “CLARiiON Open”
- Array CommPath = “Enabled” or 1
ESX Server Configuration : - Set the following Advanced Settings for the ESX Server:
- Set Disk.UseLunReset to 1
- Set Disk.UseDeviceReset to 0
You can also do this on the command line:
#Commandline -> esxcfg-advcfg -s 1 /Disk/UseLunReset
#Commandline -> esxcfg-advcfg -s 0 /Disk/UseDeviceReset
A multipathing policy of Most Recently Used must be set for all LUNs hosting clustered disks for active-passive arrays. A multipathing policy of Most Recently Used or Fixed may be set for LUNs on active-active arrays. All FC HBAs must be of the same model.
Further This means that when a SCSI bus is reset all SCSI reservations are cleared, not for one specific LUN but for the complete device.