We have a test cluster setup with MPIO and all seems to be working well. The setup is using Windows Server 2012 r2 with a qnap as the backend storage.

Routes are as follows; (qnap port 1) (qnap port 2)

Traffic flows perfectly over each switch with the failover link using MPIO working fine. The issue we are facing is whenever we disconnect our first link to the qnap to tesy the failover (port 1) the other link kicks in fine however when we restore the link it doesn't automatically map the iSCSI target. So if link 2 (port 2) was to fail the entire cluster fails until we either reconnect the iSCSI target manually or we reboot the server.

My impression is that when a link goes down the other kicks in and once the first link is repaired it should automatically reconnect to the target?

Is there an automatic reconnect setting I'm missing?

Thanks people!


From http://technet.microsoft.com/en-us/library/ee619752(v=WS.10).aspx

Configure the MPIO Failback policy setting

If you use the Failover Only load-balancing policy setting, MPIO failback allows the configuration of a preferred I/O path to the storage, and allows automatic failback to be the preferred path if desired.

Consider the following scenario:

• The computer that is running Windows Server 2008 R2 is configured by using MPIO and has two connections to storage, Path A and Path B.

• Path A is configured as the active/optimized path, and is set as the preferred path.

• Path B is configured as a standby path.

If Path A fails, Path B is used. If Path A recovers thereafter, Path A becomes the active path again, and Path B is set to standby again.

To configure the preferred path setting

1.Open Disk Management. To open Disk Management, on the Windows desktop, click Start; in the Start Search field, type diskmgmt.msc; and then, in the Programs list, click diskmgmt.

2.Right-click the disk for which you want to change the policy setting, and then click Properties.

3.On the MPIO tab, double-click the path that you want to designate as a preferred path.

Note: The setting only works with the Failover Only MPIO policy setting.

4.Select the Preferred check box, and then click OK.

Edit: Here is some more detailed instruction on setting up MPIO specifically from QNAP:


An interesting note - Microsoft does not support NIC teaming combined with MPIO on Server 2008/R2, however, they do support their own built in NIC teaming with MPIO in 2012/R2. (i.e. if you use Microsoft's NIC teaming instead of e.g. HP's NIC teaming.)

restore connection

  • Perfect thanks! One last thing, how would one set active active so both links are used for more bandwidth?
    – dqnet
    Apr 10 '14 at 19:05
  • The 'Round-robin with a subset of paths' policy seems to get you the best of both worlds: "...DSM uses the standby paths in their order of preference. For example, given 4 paths — A, B, C, and D — A, B, and C are listed as primary paths, and D is standby path. The DSM chooses a path from A, B, and C in round-robin fashion as long as at least one of them is available. If all three fail, the DSM uses D, the standby path. If A, B, or C become available, DSM stops using D and switches to available paths among A, B, and C."
    – Ryan Ries
    Apr 10 '14 at 19:29

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