The storage multipathing policy in ESXi configures in which way ESXi uses the availiable paths his LUNs.
This article discribes the different policies und explaines how to change policies for connected LUNs. Additional I show how to change the default policies for new connected LUNs.
Storage multipathing policies
- most recently used (MRU)
ESXi use the first availiable path, which is recongnized after reboot or after attaching a new LUN.
If the active path goes down, ESXi switch to the next availiable path and resides there until the new path goes down or a manual task swtich him.
Attention: If the old path comes up again, ESXi don’t switch back to this path.
- round-robin (RR)
ESXi uses all availiable paths to loadbalance the adapter. Per default all 1000 I/Os the path would be switched.
active/passive: RR only use the paths of the active storagecontrollers.
active/active: RR uses all paths on all storagecontrollers.
Like MRU fixed mode uses one path but this path could be definedas prefered path.
If the goes down a new availiable path will be selected.
In the moment the prefered path comes up again ESXi will switch back to this path.
- fixed path with array preference
This policy could be used for all storagesystems with ALUA support.
ESXi uses a path which you could define in the storagesystem an switch it in case of a pathfailure.
Changing the path selection in vSphere client
To change the path selection for a single LUN select the LUN properties in the ESXi configuration > storage.
Under properties you can select the prefered path policy.
Changing the default policy for new LUNs
To change the default policy use SSH to connect to ESXi.
esxcli storage nmp satp list
lists the different storage array types and their standard policy.
To change e.g. the standard policy für storage type VMW_SATP_ALUA from fixed to Round-Robin (RR) the following command is necessary
esxcli storage nmp satp set -s VMW_SATP_ALUA -P VMW_PSP_RR
After rebooting the ESXi the new path policy ist active.