To cluster or not to cluster, that was the question for the ABC School District. For those of you that read through the ABC School District reference design noticed that the environment was based on Microsoft Hyper-V.  And not only that, it consisted of two distinct groupings:

  • Virtual Desktops
  • Infrastructure

Why the two groupings? Because we require different levels of availability for the virtual machines.  From the school district’s perspective, a desktop is not a server, it is a desktop. That means desktops do not require the same level of high-availability as server workloads.  The Infrastructure group is clustered, meaning that the virtual servers are critical and can be live migrated to another Hyper-V server if needed.  The Virtual Desktops group is not clustered. By splitting the components up into two different Hyper-V groupings, we can better align the technical functionality with the business requirements.

So besides the high-availability options, what else is different?  The hardware

Component Virtual Desktops
Infrastructure
Type Rack mountable (2U) Rack mountable (1U)
CPU (2) Quad-Core Intel Xeon X5550 Processors (2) Quad-Core Intel Xeon X5550 Processors
Memory 96 GB RAM 64 GB RAM
Disk (8) 72GB 15,000RPM drivesRAID 1+0 (2) 72GB 15,000RPM drivesRAID 1
Disk Controller Hardware-based with battery-backed write cache Hardware-based with battery-backed write cache
Network Embedded dual-port gigabitDual-port gigabit

NIC 1, Port 0: Host/Guest traffic

NIC 1, Port 1: Parent traffic

NIC 2, Port 0: Host/Guest Traffic

NIC 2, Port 1: Parent traffic
Embedded dual-port gigabitQuad-port gigabit

NIC 1, Port 0: Host/Guest traffic

NIC 1, Port 1: Storage traffic

NIC 2, Port 0: Host/Guest Traffic

NIC 2, Port 1: Storage traffic

NIC 2, Port 2: Parent Traffic

NIC 2, Port 3: Parent traffic

What you notice is that the virtual desktops have more disks configured, which is why the server is slightly larger (2U vs 1U).  The additional drives are because the school district plans to use local drives for the Provisioning services write cache storage instead of more expensive SAN storage (money is tight in the school district).  Based on the capacity estimates, 8 spindles should provide enough IOPS for the virtual desktops.

What else is different? The NICs.  The Infrastructure servers have two additional ports that are used for storage traffic. Because the Infrastructure group is clustered, they require shared storage in order to support live migration.  You should also notice that the two ports for the Host/Guest traffic and the two ports for the Storage traffic are on two different physical NICs.  That also provides a level of fault tolerance. If one NIC fails, the virtual servers remain available.

These were just a few of the design areas for the ABC School District.  If you want more, then I encourage you to look over the reference design as well as the other blogs on the ABC School District:

Also, if you want more details on Hyper-V design decisions, then take a look at Paul Wilson’s white paper Hyper-V Design Guide.

If you want to hear more, then attend the TechTalk on June 18th

Would you have done it differently?Let me know

Daniel
Lead Architect – Worldwide Consulting Solutions
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