MPIO on Nano Server

Applies to: Windows Server 2016

This topic introduces the use of MPIO in Nano Server installations of Windows Server 2016. For general information about MPIO in Windows Server, see Multipath I/O Overview.

Using MPIO on Nano Server

You can use MPIO on Nano Server, but with these differences:

• Only MSDSM is supported.

• The Load Balancing Policy is chosen dynamically and cannot be modified. The policy has these characteristics:

  • Default -- RoundRobin (active/active)

  • SAS HDD -- LeastBlocks

  • ALUA -- RoundRobin with Subset

• Path states (active/passive) for ALUA arrays are picked up from the target array.

• Storage devices are claimed by bus type (for example, FC, iSCSI, or SAS). When MPIO is installed on Nano Server, disks are still exposed as duplicates (one available per path) until MPIO is configured to claim and manage particular disks. The sample script in this topic will claim or unclaim disks for MPIO.

• iSCSI boot is not supported.

Enable MPIO with this Windows PowerShell cmdlet:

Enable-WindowsOptionalFeature -Online -FeatureName MultiPathIO

This sample script will allow the caller to claim or unclaim disks for MPIO by changing certain registry keys. Though you can claim other storage devices by adding them to these keys, manipulating the keys directly is not recommended.

#
#  Copyright (c) 2015 Microsoft Corporation.  All rights reserved.
#
#  THIS CODE AND INFORMATION IS PROVIDED AS IS WITHOUT WARRANTY
#  OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED
#  TO THE IMPLIED WARRANTIES OF MERCHANTABILITY AND/OR FITNESS FOR A
#  PARTICULAR PURPOSE
#

<#
.Synopsis
    This powershell script allows you to enable Multipath-IO support using Microsoft's
    in-box DSM (MSDSM) for storage devices attached by certain bus types.

    After running this script you will have to either:
    1. Disable and then re-enable the relevant Host Bus Adapters (HBAs); or
    2. Reboot the system.

.Description

.Parameter BusType
    Specifies the bus type for which the claim/unclaim should be done.

    If omitted, this parameter defaults to All.

    All - Will claim/unclaim storage devices attached through Fibre Channel, iSCSI, or SAS.

    FC - Will claim/unclaim storage devices attached through Fibre Channel.

    iSCSI - Will claim/unclaim storage devices attached through iSCSI.

    SAS - Will claim/unclaim storage devices attached through SAS.

.Parameter Server
    Allows you to specify a remote system, either via computer name or IP address.

    If omitted, this parameter defaults to the local system.

.Parameter Unclaim
    If specified, the script will unclaim storage devices of the bus type specified by the
    BusType parameter.

    If omitted, the script will default to claiming storage devices instead.

.Example
MultipathIoClaim.ps1

Claims all storage devices attached through Fibre Channel, iSCSI, or SAS.

.Example
MultipathIoClaim.ps1 FC

Claims all storage devices attached through Fibre Channel.

.Example
MultipathIoClaim.ps1 SAS -Unclaim

Unclaims all storage devices attached through SAS.

.Example
MultipathIoClaim.ps1 iSCSI 12.34.56.78

Claims all storage devices attached through iSCSI on the remote system with IP address 12.34.56.78.

#>
[CmdletBinding()]
param
(
    [ValidateSet('all','fc','iscsi','sas')]
    [string]$BusType='all',

    [string]$Server=127.0.0.1,

    [switch]$Unclaim
)

#
# Constants
#
$type = [Microsoft.Win32.RegistryHive]::LocalMachine
[string]$mpioKeyName = SYSTEM\CurrentControlSet\Control\MPDEV
[string]$mpioValueName = MpioSupportedDeviceList
[string]$msdsmKeyName = SYSTEM\CurrentControlSet\Services\msdsm\Parameters
[string]$msdsmValueName = DsmSupportedDeviceList

[string]$fcHwid = MSFT2015FCBusType_0x6
[string]$sasHwid = MSFT2011SASBusType_0xA
[string]$iscsiHwid = MSFT2005iSCSIBusType_0x9

#
# Functions
#

function AddHardwareId
{
    param
    (
        [Parameter(Mandatory=$True)]
        [string]$Hwid,

        [string]$Srv=127.0.0.1,

        [string]$KeyName=SYSTEM\CurrentControlSet\Control\MultipathIoClaimTest,

        [string]$ValueName=DeviceList
    )

    $regKey = [Microsoft.Win32.RegistryKey]::OpenRemoteBaseKey($type, $Srv)
    $key = $regKey.OpenSubKey($KeyName, 'true')
    $val = $key.GetValue($ValueName)
    $val += $Hwid
    $key.SetValue($ValueName, [string[]]$val, 'MultiString')
}

function RemoveHardwareId
{
    param
    (
        [Parameter(Mandatory=$True)]
        [string]$Hwid,

        [string]$Srv=127.0.0.1,

        [string]$KeyName=SYSTEM\CurrentControlSet\Control\MultipathIoClaimTest,

        [string]$ValueName=DeviceList
    )

    [string[]]$newValues = @()
    $regKey = [Microsoft.Win32.RegistryKey]::OpenRemoteBaseKey($type, $Srv)
    $key = $regKey.OpenSubKey($KeyName, 'true')
    $values = $key.GetValue($ValueName)
    foreach($val in $values)
    {
        # Only copy values that don't match the given hardware ID.
        if ($val -ne $Hwid)
        {
            $newValues += $val
            Write-Debug $($val) will remain in the key.
        }
        else
        {
            Write-Debug $($val) will be removed from the key.
        }
    }
    $key.SetValue($ValueName, [string[]]$newValues, 'MultiString')
}

function HardwareIdClaimed
{
    param
    (
        [Parameter(Mandatory=$True)]
        [string]$Hwid,

        [string]$Srv=127.0.0.1,

        [string]$KeyName=SYSTEM\CurrentControlSet\Control\MultipathIoClaimTest,

        [string]$ValueName=DeviceList
    )

    $regKey = [Microsoft.Win32.RegistryKey]::OpenRemoteBaseKey($type, $Srv)
    $key = $regKey.OpenSubKey($KeyName)
    $values = $key.GetValue($ValueName)
    foreach($val in $values)
    {
        if ($val -eq $Hwid)
        {
            return 'true'
        }
    }

    return 'false'
}

function GetBusTypeName
{
    param
    (
        [Parameter(Mandatory=$True)]
        [string]$Hwid
    )

    if ($Hwid -eq $fcHwid)
    {
        return Fibre Channel
    }
    elseif ($Hwid -eq $sasHwid)
    {
        return SAS
    }
    elseif ($Hwid -eq $iscsiHwid)
    {
        return iSCSI
    }

    return Unknown
}

#
# Execution starts here.
#

#
# Create the list of hardware IDs to claim or unclaim.
#
[string[]]$hwids = @()

if ($BusType -eq 'fc')
{
    $hwids += $fcHwid
}
elseif ($BusType -eq 'iscsi')
{
    $hwids += $iscsiHwid
}
elseif ($BusType -eq 'sas')
{
    $hwids += $sasHwid
}
elseif ($BusType -eq 'all')
{
    $hwids += $fcHwid
    $hwids += $sasHwid
    $hwids += $iscsiHwid
}
else
{
    Write-Host Please provide a bus type (FC, iSCSI, SAS, or All).
}

$changed = 'false'

#
# Attempt to claim or unclaim each of the hardware IDs.
#
foreach($hwid in $hwids)
{
    $busTypeName = GetBusTypeName $hwid

    #
    # The device is only considered claimed if it's in both the MPIO and MSDSM lists.
    #
    $mpioClaimed = HardwareIdClaimed $hwid $Server $mpioKeyName $mpioValueName
    $msdsmClaimed = HardwareIdClaimed $hwid $Server $msdsmKeyName $msdsmValueName
    if ($mpioClaimed -eq 'true' -and $msdsmClaimed -eq 'true')
    {
        $claimed = 'true'
    }
    else
    {
        $claimed = 'false'
    }

    if ($mpioClaimed -eq 'true')
    {
        Write-Debug $($hwid) is in the MPIO list.
    }
    else
    {
        Write-Debug $($hwid) is NOT in the MPIO list.
    }

    if ($msdsmClaimed -eq 'true')
    {
        Write-Debug $($hwid) is in the MSDSM list.
    }
    else
    {
        Write-Debug $($hwid) is NOT in the MSDSM list.
    }

    if ($Unclaim)
    {
        #
        # Unclaim this hardware ID.
        #
        if ($claimed -eq 'true')
        {
            RemoveHardwareId $hwid $Server $mpioKeyName $mpioValueName
            RemoveHardwareId $hwid $Server $msdsmKeyName $msdsmValueName
            $changed = 'true'
            Write-Host $($busTypeName) devices will not be claimed.
        }
        else
        {
            Write-Host $($busTypeName) devices are not currently claimed.
        }

    }
    else
    {
        #
        # Claim this hardware ID.
        #
        if ($claimed -eq 'true')
        {
            Write-Host $($busTypeName) devices are already claimed.
        }
        else
        {
            AddHardwareId $hwid $Server $mpioKeyName $mpioValueName
            AddHardwareId $hwid $Server $msdsmKeyName $msdsmValueName
            $changed = 'true'
            Write-Host $($busTypeName) devices will be claimed.
        }
    }
}

#
# Finally, if we changed any of the registry keys remind the user to restart.
#
if ($changed -eq 'true')
{
    Write-Host The system must be restarted for the changes to take effect.
}