Live Migration over SMB Direct leaves more CPU cycles for Virtual RSS (vRSS) in Windows Server 2012 R2

I recently (January 22nd 2014) gave a WebCast presentation for the Dutch Windows Management User Group (@WMUG_NL) in which I made the case for using SMB Direct with Live Migration to save CPU cycles other (VM) workloads. There are several areas where the CPU cycles are better spent but I used vRSS to show case one scenario.

We’re using a 2 node Windows Server 2012 R2 Hyper-V cluster on Dell PowerEdge R720 servers with Mellanox ConnectX-3 (CSV  &  live migration) and Intel X520-DA (Hyper-V switch), all 10Gbps.

This is what a CPU bottleneck looks like that can be solved by using vRSS in Windows Server 2012 R2.image

The host machines are Hyper Threading enabled. The virtual switch is attached to a switch independent NIC team with dynamic mode. In this setup it’s normal that the sending VM is leveraging both members while the receiving VM traffic is coming in over one member of the host team.

No let’s enable vRSS in the VM and see what this does for this picture.image

Pretty impressive isn’t it. DidierTest03 is the sending VM running on host A and DidierTest04 is the receiving VM that has vRSS enabled and is running on Host B. For vRSS you need both hosts and VMs to run Windows Server 2012 or Windows 8.1. You can see the load is spread across 7 vCPUs in the VM. DidierTest04 has 8 vCPUs. I configured vRSS in the VM to be able to use 7 vCPUs and leave vCPU 0, the default one, alone to handle those workloads.

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Given multiple Logical CPUs & vCPUs we can get line speed with 10Gbps inside a virtual machine. This, ladies and gentlemen is a thing of beauty.

Now tell me, if you have business related needs for those CPU cycles why would you not offload the work that needs to be done for live migration to the NIC via SMB direct? This is about getting maximum VM density, performance & ROI form your infrastructure, whilst saving on servers, power and cooling. When you see the smile on your clients or bosses face, just say “you’re welcome” and smile back Open-mouthed smile.

Live Migration over NIC Team in Switch Independent Mode With Dynamic Load Balancing & Compression in Windows Server 2012 R2

In a previous blog post Live Migration over NIC Team in Switch Independent Mode With Dynamic Load Balancing & TCP/IP in Windows Server 2012 R2 we looked at what Dynamic load balancing mode in NIC teaming can do for us . Especially in a switch independent configuration as until now there was no possibility to leverage the complete bandwidth provided by the NIC team when migrating between only 2 nodes. I that blog we used TCP/IP. Now we’ll configure Compression and see what that does for us.

So we set up a NIC team in switch independent mode with Dynamic load balancing, it’s identical as that one used for the tests with TCP/IP.

Compression basically slashes the live migration times in half at a cost. CPU cycles.And again with Dynamic load balancing we can now also use all member of a NIC team for live migration even in switch independent mode. The speeds for live migrating 6 VMs  with 9GB of memory simultaneously were 12-14 seconds.

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Take a look at the screen shot above. You see 6 VMs coming in to the host where these counters are collected and after that you see them being live migrated away from the host. As we have plenty of idle cycles I this test lab they get used, both when being the target and the source of the VMs being live migrated. You can also see that a lot less bandwidth is needed to achieve a faster live migration experience (compared to TCP/IP).

By the looks of it the extra bandwidth will help out when we have less CPU and vice versa. This is both the case for a single NIC or teamed NICs. Do note that you cannot combine compression with Multichannel. That means that the only scenario allowing for multiple NICs to be used with compression is NIC teaming. When you have a bunch  of free 1Gbps NICs in surplus this might get things moving for you!

Interesting stuff. I’m really looking forward to the moment we can run production loads on these configurations …

Live Migration over NIC Team in Switch Independent Mode With Dynamic Load Balancing & TCP/IP in Windows Server 2012 R2

As you can imagine I was quite interested in seeing what the new Dynamic load balancing mode in NIC teaming can do for us. Especially in a switch independent configuration as until now there was no possibility to leverage the complete bandwidth provided by the NIC team when migrating between only 2 nodes.

So we set up  a NIC team in switch independent mode with Dynamic load balancing. Here’s a screenshot of the NIC team setup. LM is the NIC team I’m using for some live migration testing.image

For these tests we used TCP/IP to do the live migrations. I’ll be sharing the compression & Multichannel performance option results in a later blog and do some comparisons. But for now I can inform you that with Dynamic load balancing we can now also use all member of a NIC team for live migration even in switch independent mode. I’m a fan of switch independent mode. Now possibly even more. Speeds for live migrating 6 VMs simultaneously with 9GB of memory were 28-30 seconds.image

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The CPU load not very low but RSS does it’s job to spread it out.image

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Now the beauty of al this is that this had no negative impact due to out of order packets. For one a single live migration sticks to a single team member. Here’s a screenshot of a single VM live migrated over a NIC Team with Dynamic load balancing.image

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As you can see there will not be out of order packets in this case.

Secondly the Dynamic load balancing mode is based on the “flowlets”. This means that the impact due to out or order /reordering of TCP/IP packets is minimal.

I also refer you to the following article Dynamic Load Balancing Without Packet Reordering.The conclusion is quite interesting:

We have introduced the concept of flowlet-switching and developed an algorithm which utilizes flowlets in traffic splitting. Our work reveals several interesting conclusions. First,highly accurate traffic splitting can be implemented with little to no impact on TCP packet reordering and with negligible state overhead. Next, flowlets can be used to make load balancing more responsive, and thus help enable a new generation of real-time adaptive traffic engineering. Finally, the existence and usefulness of flowlets show that TCP burstiness is not necessarily a bad thing, and can in fact be used advantageously.

And now as a show closer let’s do live migrations between both hosts in both directions.image

Speed people, in live migration is a thing of beauty. Microsoft is really providing us with lots of options. This is good. We can use what’s available, where available, when available and make sure we get the best possible solution and performance whatever the environment and budget.

Configuring Performance Options for Live Migration In Windows Server 2012 R2 Preview

New Options For Optimizing Live Migrations

In Windows Server 2012 R2 we have a whole range of options to leverage Live Migration of our environment and needs. Next to the new default (Compression) we can now also leverage SMB 3.0 (Multichannel, RDMA) for all forms of Live Migration and not just for Shared Nothing Live Migration  (see  Shared Nothing Live Migration Leverages SMB 3.0 Under the Hood) or Storage Live Migration when both the source and the target are SMB 3.0 storage.

TCP/IP

Here you can use a one NIC or a NIC Team for bandwidth aggregation for live migration (see  Teamed NIC Live Migrations Between Two Hosts In Windows Server 2012 Do Use All Members). This is the process you have known in Windows Server 2012. You can select multiple NICs or even Teams of NICs  but only one of those (one NIC or one Team) will be used. The other(s)will only be used when the first one is not available.

Compression

This option leverages spare CPU cycles to compress the memory contents of virtual machines being migrated. Only then is it sent over the wire via TCP/IP connection. This speeds up the Live Migration Process. This process is CPU load aware so it will only use idle cycles to protect the workload on the hosts. This is the default setting in Hyper-V running on Windows Server 2012 R2 Preview.

SMB

This setting will leverage two SMB 3.0 features. Multichannel and, if supported by and for the NICs involved, RDMA.

  • SMB Direct (RDMA) will be used when the network adapters of both the source and destination servers have Remote Direct Memory Access (RDMA) capabilities enabled.
  • SMB Multichannel will automatically detect and use multiple connections when a proper SMB Multichannel configuration is identified.

Where to set these options?

In Hyper-V Manager go to “Hyper-V Settings” in the Actions pane.image

Expand the Live Migrations node under Server in the left pane (click the “+”) and select to “Advanced Features”.image

Select the option desired under" “Performance Options”.image

Happy testing!

 

EDIT: Aidan Finn posted the PowerShell commands to configure the performance options in Configuring WS2012 R2 Hyper-V Live Migration Performance Options Using PowerShell The MVP community at work & it rocks Smile