2011
09.16

If you asked me, any Hyper-V expert, or Microsoft that question about Windows Server 2008 R2 then it was easy: either 4 or 6 (or 8 or 10 with NIC teaming) depending if you used iSCSI (2 NICs with MPIO) or not.  Ask that question with Windows Server 8 and the answer is … it depends.

You do have several roles that need to be serviced with network connections:

  • Parent
  • Cluster/Storage
  • Live Migration
  • Hyper-V Extensible Switch (note that what we called virtual network is now virtual switch – a virtual network is an abstraction or virtualisation now.  This is probably serviced by 2 NICs with NIC teaming (by Windows)

How this connections are physically presented to the network really does depend on the hardware in your server, whether you need physical fabric isolation or not (trend is to fabric convergence to reduce physical fabrics complexity and cost), and whether you want to enable NIC teaming or not.

Here’s a converged example from yesterday’s Build Windows sessions that uses fault tolerant 10 GbE NICs (teamed by Windows Server 8). 

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All of the networking functions all have port connections into the Hyper-V Extensible Switch.  The switch is bound to two 10 GbE network adapters in the host server.  NIC teaming provides network path fault tolerance (in my experience a switch is more likely to die than a NIC now).  QoS ensures that each connection gets the necessary bandwidth – I reckon the minimum bandwidth option is probably best here because it provides a service guarantee and allows burst when capacity is available.  Port ACLs can be used to control what a connection can connect to – to provide network isolation.

The reason that MSFT highlighted this example is because it is a common hardware configuration now.  If you buy HP blades, you can do some of this now with their Flex10 solution.  Microsoft are recommending 10 GbE for future proofing, and you can use 2 NICs and physical switch ports with NIC teaming and network fault tolerance, instead of using 10 NICs and 10 switch ports for the 1 GbE alternative!

A lot of examples were shown.  This one goes down a more traditional route with physical isolation:

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Most servers come with 4 * 1 GbE NICs by default.  You could take the above example, and use just 1 * 1 GbE NIC for the Hyper-V Extensible switch if budget was an issue, but you’d lose NIC teaming.  You could add NIC teaming to that example by adding another 1 GbE NIC (now giving a total of 5 * 1 GBe NICs).

The answer to the “how many NICs” question is, fortunately and unfortunately, a consultants answer: it depends.

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