Windows Server 2012 and Multipath I/O to Storage Area Network

Recently, I was assigned the task of performing a hardware refresh in the datacenter. The previous Windows 2008 systems were connected to the SAN via fiber channel HBA’s and among other thing, had PowerPath installed in order to provide sufficient failover and load balancing to a VNX. When the new equipment was purchased, part of the refresh was a migration to Windows Server 2012 R2 using Emulex FCoE adapters for connectivity.

Once the operating system was installed, I went to the Emulex website to download the appropriate drivers and network teaming software. However, I could not locate a download for the teaming software for Windows Server 2012 R2. After trying various methods, I noticed a notation at the bottom of the screen indicating that for Windows Server 2012 R2, the built-in services were to be used.

Further research found that Microsoft has also built in multipath services into the 2012 R2 product. While there may be varying opinions on the need, it appears that PowerPath is no longer required when using the new Windows Server operating systems. However, if you still chose to use PowerPath, the minimal version needed will be PowerPath 5.7 SP2. Otherwise, the instructions below will walk you through configuring the MPIO feature in Windows Server 2012 for multipath failover in a SAN environment. 

The first step is the installation of the MPIO feature. To install this feature from the dashboard, click on the “Add Roles and Features” selection. 

Click the “Next” radio button until you reach the “Feature” selection page. You may need to scroll down to see the “Multipath I/O” option. Once you have located it, click the box beside it and ensure a check mark appears, then click “Next”.

On the confirmation page, you can select to automatically reboot the server, but this feature does not require a reboot. Click “Install” to complete the installation of the feature. 

Once the feature has been installed, there will be a new option under the administrative tools called “MPIO”. Click on this icon to launch the configuration page. 

In order to determine the devices, select the “Discover Multi-Paths” tab at the top of the screen. The top box will show those devices that support ALUA failover. In the example below, the EMX VNX is seen as a “DGC VRAID” device. If the SAN includes SAS drives, I have found that support for SAS devices should also be selected. 

If you do not see any devices, it may be necessary to launch a PowerShell or command prompt and run a manual claim command. Either of these MUST be an administrative level executions. The command is “mpclaim.exe –e” and will show the detected storage systems. If this command does not produce any results, then the server is not seeing the storage system or it is unsupported. 

Once you click “OK” the devices are installed (this can take several minutes with no indicator) and a reboot is required. 

Once the server has completed rebooting, log into the system either launch Server or Computer Manager and examine the disk. At this point, you should see only one drive per LUN presented to the server. However, if you see two sets of disk, a series of those online and those offline.

In this case, you will need to re-run the MPIO configurator and include non-ALUA devices except for the internal controller. In the example below, there is a “DGC LUNZ” device. This specific device applies to EMC storage and is typically due to the host not being in a storage group. However, in my case, the devices were in the correct storage group. So, add the second device and allow the server to reboot. 


Once the second reboot is complete, examine the disk configuration. There should only be one volume shown for each LUN presented to the server. Also, if you launch the MPIO utility, all of the devices that have been added should now appear in the “MPIO Devices” tab. 

Here is an explanation of the devices listed as a reference:

• DGC LUNZ – DGC is an acronym for Data General Corporation which was purchased by EMC. LUNZ is a logical device that replaces LUN0 allow data to pass to the array.
• DGC VRAID – While the DGC is the same as above, the VRAID means it detects a LUN spread over several disk in an array
• MSFT2011SASBUSType_0xA – This refers to the version of Microsoft’s SAS BUS adapter device.
• Vendor 8Product 16 – This value is nothing more than a placeholder that shows the correct formatting for the vendor and products.

However, if you select the “Discover Multi-Paths” tab, the local array controller should still be listed. In this case, it is a HP controller on a HP server. You should not attempt to add these types of local devices to the devices. 


As you can see, configuring MPIO for Windows Server 2012 R2 is rather straight forward. It eliminates the need for additional software and licensing for each host that has been needed on older operating systems, therefore saving the company additional expenses.