1 Reply Latest reply on Mar 30, 2018 12:32 PM by LucD

    Path Selection Policy Question

    aatef6 Novice

      Hello Experts,

       

      I have a question about how does the PSP works. We have the below SATP list that should enforce EMC Symmetrix SAN to a default PSP of RoundRobin policy. Then i have decided to make a test of manually changing the LUNs multipath policy to Fixed then reboot the host to make sure it will come up and re-establish the LUN connection so it will apply the default PSP which is RR. However, it seems the default PSP was not applied and the LUN connection came up again as fixed with the same preferred path. Does anyone know if that's the expected behavior or if there is something wrong with my config? Below are the detailed steps. Thanks

       

      [root@ESXi:~] esxcli storage nmp satp rule list | grep -i emc

      VMW_SATP_SYMM                EMC      SYMMETRIX                                                        system                                                                     EMC Symmetrix

      VMW_SATP_INV                 EMC      Invista                                                          system                                              

      VMW_SATP_INV                 EMC      LUNZ                                                             system                                                                     Invista LUNZ

       

      [root@ESXi:~] esxcli storage nmp satp list

      Name                 Default PSP    Description

      -------------------  -------------  ------------------------------------------

      VMW_SATP_SYMM        VMW_PSP_RR     Supports EMC Symmetrix

      VMW_SATP_MSA         VMW_PSP_MRU    Placeholder (plugin not loaded)

      VMW_SATP_ALUA        VMW_PSP_MRU    Placeholder (plugin not loaded)

      VMW_SATP_DEFAULT_AP  VMW_PSP_MRU    Placeholder (plugin not loaded)

      VMW_SATP_SVC         VMW_PSP_FIXED  Placeholder (plugin not loaded)

      VMW_SATP_EQL         VMW_PSP_FIXED  Placeholder (plugin not loaded)

      VMW_SATP_INV         VMW_PSP_FIXED  Placeholder (plugin not loaded)

      VMW_SATP_EVA         VMW_PSP_FIXED  Placeholder (plugin not loaded)

      VMW_SATP_ALUA_CX     VMW_PSP_RR     Placeholder (plugin not loaded)

      VMW_SATP_CX          VMW_PSP_MRU    Placeholder (plugin not loaded)

      VMW_SATP_LSI         VMW_PSP_MRU    Placeholder (plugin not loaded)

      VMW_SATP_DEFAULT_AA  VMW_PSP_FIXED  Supports non-specific active/active arrays

      VMW_SATP_LOCAL       VMW_PSP_FIXED  Supports direct attached devices

      [root@ESXi:~]

       

      Below is how the LUN looked like before change

       

      [root@ESXi:~] esxcli storage nmp device list

      naa.60000970000192605421533033423833

         Device Display Name: EMC iSCSI Disk (naa.60000970000192605421533033423833)

         Storage Array Type: VMW_SATP_SYMM

         Storage Array Type Device Config: {action_OnRetryErrors=off}

         Path Selection Policy: VMW_PSP_RR

         Path Selection Policy Device Config: {policy=rr,iops=1000,bytes=10485760,useANO=0; lastPathIndex=2: NumIOsPending=0,numBytesPending=0}

         Path Selection Policy Device Custom Config:

         Working Paths: vmhba1:C0:T0:L3, vmhba1:C0:T1:L3, vmhba2:C0:T0:L3, vmhba2:C0:T1:L3

         Is USB: false

       

      i have then decided to manually change this LUN to fixed using this script that i have created. Below is an excerept of the script using PowerCLI

       

      $lunpath =(get-vmhosthba -VMhost $vmhost -Type IScsi | get-scsilun $lun | get-scsilunpath | Where-Object {$_.State -like "Active"} | Where-Object {$_.Name -match "$device"} | Select-Object -first 1).Name

      if ($lunpath){

      Get-VMHost $vmhost | Get-ScsiLun $lun| Set-Scsilun -MultiPathPolicy Fixed -PreferredPath $lunpath

       

      Below is how the LUN looked like after change, Fixed with a preferred path

       

      [root@ESXi:~] esxcli storage nmp device list

      naa.60000970000192605421533033423833

         Device Display Name: EMC iSCSI Disk (naa.60000970000192605421533033423833)

         Storage Array Type: VMW_SATP_SYMM

         Storage Array Type Device Config: {action_OnRetryErrors=off}

         Path Selection Policy: VMW_PSP_FIXED

         Path Selection Policy Device Config: {preferred=vmhba1:C0:T1:L3;current=vmhba1:C0:T1:L3}

         Path Selection Policy Device Custom Config:

         Working Paths: vmhba1:C0:T1:L3

         Is USB: false

       

      I have then decided to reboot the host to make sure that as soon as it comes up, the ESXi will set the LUN PSP to RoundRobin as illustrated by the default PSP in the SATP list, however,  i was surprised to find it still set to Fixed untill i manually changed it back to RoundRobin.

       

      [root@ESXi:~]  esxcli storage nmp device list

      naa.60000970000192605421533033423833

         Device Display Name: EMC iSCSI Disk (naa.60000970000192605421533033423833)

         Storage Array Type: VMW_SATP_SYMM

         Storage Array Type Device Config: {action_OnRetryErrors=off}

         Path Selection Policy: VMW_PSP_FIXED

         Path Selection Policy Device Config: {preferred=vmhba1:C0:T1:L3;current=vmhba1:C0:T1:L3}

         Path Selection Policy Device Custom Config:

         Working Paths: vmhba1:C0:T1:L3

         Is USB: false

       

      Does anyone know why the PSP did not change to the default RR policy after reboot? is there anything wrong with my config? Thanks