The Hitch Hikers Guide to Hyper-V Administration: Don’t Panic

Not all information you might see or is presented to you is valid. You need to check, that’s the prime reason we have the “trust but verify” mantra in IT. If you don’t you might start trouble shooting a ghost issue. An example of this are GUI issues, such as when you leave the Hyper-V Manager GUI open for way to long and the information goes stale in the cache.

The below screen shot is what caused some diligent admins to start trouble shooting a non existent problem. The figured that the VMs were left in a locked state due to backups failing. But hey, all backups had run and succeeded?! So they searched and found  KB article 2964439 Hyper-V virtual machine backup leaves the VM in a locked state. When they wanted to install the hotfix it failed stating it was not applicable to their system.

At that moment they considered killing the VMMS.exe service and/or failing over the nodes. While preparing for that they’d logged in to all nodes, only to see the issue not present there. That made ‘m think and step back for a while.


In this case it’s just a quirk with the Hyper-V manager that is left open way to long. Right click the host and refresh or close the GUI and reopen it is all that’s needed to see the real information.

So slow down before you start trouble shooting & recovering form a “ghost” problem. It may cause real issues. The lesson here is you should not go into the “Action Jackson” mode. You can move swift and efficient but the ability to execute does not constitute just speed it doing what’s needed when and when needed. Here ends the lesson Smile

Windows Server 2016 Technical Preview Version 3 Cluster Upgrades

I was eagerly awaiting the release of Windows Server 2016 Technical Preview 3 for further experimenting and testing and August 19th 2015was the big day with a truck load of announcements and press releases including the arrival of TPv3 which also made containers publicly available for testing to all of us.


After a swift download II set out upgrading the labs, both PC hardware based and enterprise grade server hardware. I always test out the less wise things as well just to kick the tires and test behavior left and right.

As always I tested some in place upgrades just to see how well that goes before doing clean installs . Not recommend in production but hey,Testing is good. At first all networking seem to be OK but it wasn’t. So I ended up with doing clean installs which are advisable, even more so with non production versions of the OS. The product is not finished yet! This is also the supported way of doing a new cluster build. imageThe end result is a lab at home on PC hardware and an enterprise grade lab to work with in the datacenter. Busy times ahead.

For help on what’s new in this build go here What’s New in Windows Server 2016 Technical Preview 3 and good luck on your Windows Server 2016 Technical Preview Version 3 cluster upgrades!

Happy testing!

High performance live migration done right means using SMB Direct

I  saw people team two 10GBps NICs for live migration and use TCP/IP. They leveraged LACP for this as per my blog Teamed NIC Live Migrations Between Two Hosts In Windows Server 2012 Do Use All Members . That was a nice post but not a commercial to use it. It was to prove a point that LACP/Static switch dependent teaming did allow for multiple VMs to be live migrated in the same direction between two node. But for speed, max throughput & low CPU usage teaming is not the way to go. This is not needed as you can achieve bandwidth aggregation and redundancy with SMB via Multichannel. This doesn’t require any LACP configuration at all and allows for switch independent aggregation and redundancy. Which is great, as it avoids stacking with switches that don’t do  VLT, MLAG,  …

Even when your team your NICs your better off using SMB. The bandwidth aggregation is often better. But again, you can have that without LACP NIC teaming so why bother? Perhaps one reason, with LACP failover is faster, but that’s of no big concern with live migration.

We’ll do some simple examples to show you why these choices matter. We’ll also demonstrate the importance of an optimize RSS configuration. Do not that the configuration we use here is not a production environment, it’s just a demo to show case results.

But there is yet another benefit to SMB.  SMB Direct.  That provides for maximum throughput, low latency and low CPU usage.

LACP NIC TEAM with 2*10Gbps with TCP

With RSS setting on the inbox default we have problems reaching the best possible throughput (17Gbps). But that’s not all. Look at the CPU at the time of live migration. As you can see it’s pretty taxing on the system at 22%.


If we optimize RSS with 8 RSS queues assigned to 8 physical cores per NIC on a different CPU (dual socket, 8 core system) we sometimes get better CPU overhead at +/- 12% but the throughput does not improve much and it’s not very consistent. It can get worse and look more like the above.


LACP NIC TEAM with 2*10Gbps with SMB (Multichannel)

With the default RSS Settings we still have problems reaching the best possible throughput but it’s better (19Gbps). CPU wise, it’s pretty taxing on the system at 24%.


If we optimize RSS with 8 RSS queues assigned to 8 physical cores per NIC on a different CPU (dual socket, 8 core system) we get better over CPU overhead at +/- 8% but the throughput actually declined (17.5 %). When we run the test again we were back to the results we saw with default RSS settings.


Is there any value in using SMB over TCP with LACP for live migration?

Yes there is. Below you see two VMs live migrate, RSS is optimized. One core per VM is used and the throughput isn’t great, is it. Depending on the speed of your CPU you get at best 4.5 to 5Gbps throughput per VM as that 1 core per VM is the limiting factor. Hence see about 9Gbps here, as there’s 2 VMs, each leveraging 1 core.


Now look at only one VM with RSS is optimized with SMB over an LACP NIC team. Even 1 large memory VM leverages 8 cores and achieves 19Gbps.


What about Switch Independent Teaming?

Ah well that consumes a lot less CPU cycles but it comes at the price of speed. It has less CPU overhead to deal with in regards to LACP. It can only receive on one team member. The good news is that even a single VM can achieve 10Gbps (better than LACP) at lower CPU overhead. With SMB you get better CPU distribution results but as the one member is a bottle neck, not faster. But … why bother when we have …better options!? Read on Smile!

No Teaming – 2*10Gbps with SMB Multichannel, RSS Optimized

We are reaching very good throughput but it’s better (20Gbps) with 8 RSS queues assigned to 8 physical cores. The CPU at the time of live migration is pretty good at 6%-7%.


Important: This is what you want to use if you don’t have 10Gbps but you do have 4* 1Gbps NICs for live migration. You can test with compression and LACP teaming if you want/can to see if you get better results. Your mirage may vary Smile. If you have only one 1Gbps NIC => Compression is your sole & only savior.

2*10Gbps with SMB Direct

We’re using perfmon here to see the used bandwidth as RDMA traffic does not show up in Task Manager.


We have no problems reaching the best possible throughput but it’s better (20Gbps, line speed). But now look at the CPU during live migration. How do you like them numbers?

Do not buy non RDMA capable NICs or Switches without DCB support!

These are real numbers, the only thing is that the type and quality of the NICs, firmware and drivers used also play a role an can skew the results a bit. The onboard LOM run of the mill NICs aren’t always the best choice. Do note that configuration matters as you have seen. But SMB Direct eats them all for breakfast, no matter what.

Convinced yet? People, one of my core highly valuable skillsets is getting commodity hardware to perform and I tend to give solid advice. You can read all my tips for fast live migrations here in Live Migration Speed Check List – Take It Easy To Speed It Up

Does all of this matter to you? I say yes , it does. It depends on your environment and usage patterns. Maybe you’re totally over provisioned and run only very small workloads in your virtual machines. But it’s save to say that if you want to use your hardware to its full potential under most circumstances you really want to leverage SMB Direct for live migrations. What about that Hyper-V cluster with compute and storage heavy applications, what about SQL Server virtualization? Would you not like to see this picture with SMB RDMA? The Mellanox  RDMA cards are very good value for money. Great 10Gbps switches that support DCB (for PFC/ETS) can be bought a decent prices. You’re missing out and potentially making a huge mistake not leveraging SMB Direct for live migrations and many other workloads. Invest and design your solutions wisely!

DELL Microsoft Storage Spaces Offerings

Dell was the 1st OEM to actively support and deliver Microsoft Storage Spaces solutions to its customers.


They recognized the changing landscape of storage and saw that this was one of the option customers are interested in. When DELL adds their logistical prowess and support infrastructure into the equation it helps deliver Storage Spaces to more customers. It removes barriers.

In June 2015 DELL launched their newest offering based on generation 13 hardware.


Recently DELL has published it’s docs and manuals for Storage Spaces with the MD1420 JBOD Storage Spaces with the MD1420 JBOD

You can find some more information on DELL storage spaces here and here.

I’m looking forward to what they’ll offer in 2016 in regards to Storage Spaces Direct (S2D) and networking (10/25/40/50/100Gbps). I’m expecting that to be a results of some years experience combined with the most recent networking stack and storage components. 12gbps SAS controller, NVMe options in Storage Spaces Direct. Dell has the economies of scale & knowledge to be one of the best an major players in this area. Let’s hope they leverage this to all our advantage. They could (and should) be the first to market with the most recent & most modern hardware to make these solutions shine when Windows Server 2016 RTM somewhere next year.