What Impact on You Will AMD EPYC Processors Have?

Microsoft has announced new HB-V2, Das_v3, and Eas_v3 virtual machines based on hosts with AMD EPYC processors. What does this mean to you and when should you use these machines instead of the Intel Xeon alternatives?

A is for AMD

The nomenclature for Azure virtual machines is large. It can be confusing for those unfamiliar with the meanings. When I discussed the A-Series, the oldest of the virtual machine series, I would tell people “A is the start of the alphabet” and discuss these low power machines. The A-Series was originally hosted on physical machines with AMD Opteron processors, a CPU that had lots of cores and required little electricity when compared to the Intel Xeon competition. These days, an A-Series might actually be hosted on hosts with Intel CPUs, but each virtual processor is throttled to offer similar performance to the older hosts.

Microsoft has added the AMD EPYC 7002 family of processors to their range of hosts, powering new machines:

  • HB_v2: A high performance compute machine with high bandwidth between the CPU and RAM.
  • Das_v3 (and Da_v3): A new variation on the Ds_v3 that offers fast disk performance that is great for database virtual
  • Eas_v3 (and Ea_v3): Basically the Das_v3 with extra

EPYC Versus Xeon

The 7002 or “Rome” family of EPYC processors is AMD’s second generation of this type of processor. From everything I have read, this generation of the processor family firmly returns AMD back into the data centre.

I am not a hardware expert, but some things really stand out about the EPYC, which AMD claims is revolutionary about how it focuses on I/O, which pretty important for services such as databases (see the Ds_v3/Es_v3 core scenarios). EPYC uses PCI Gen 4 which is double the performance of Gen 3 which Intel still uses. That’s double the bus to storage … great for disk performance. The EPYC gets offers 45% faster RAM access than the Intel option … hence Microsoft’s choice for the HB_v2. If you want to get nerdy, then there are fewer NUMA nodes per socket, which reduces context switches for complex RAM v process placement scenarios.

Why AMD Now?

There have been rumours that Microsoft hasn’t been 100% happy with Intel for quite a while. Everything I heard was in the PC market (issues with 4th generation, battery performance, mobility, etc). I have not heard any rumours of discontent between Azure and Intel – in fact, the DC-Series virtual machine exists because of cooperation between the two giant technology corporations on SGX. But two things are evident:

  • Competition is good
  • Everything you read about AMD’s EPYC makes it sound like a genuine Xeon killer. As AMD says, Xeon is a BMW 3-series and EPYC is a Tesla – I hope the AMD build quality is better than the American-built EV!
  • As is often the case, the AMD processor is more affordable to purchase and to power – both big deals for a hosting/cloud company.

Choosing Between AMD and Xeon

OK, it was already confusing which machine to choose when deploying in Azure … unless you’ve heard me explain the series and specialisation meanings. But now we must choose between AMD and Intel processors!

I was up at 5 am researching so this next statement is either fuzzy or was dreamt up (I’m not kidding!): it appears that for multi-threaded applications, such as SQL Server, then AMD-powered virtual machines are superior. However, even in this age-of-the-cloud, single threaded applications are still running corporations. In that case, (this is where things might be fuzzy) an Intel Xeon-powered virtual machine might be best. You might think that single-threaded applications are a thing of the past but I recently witnessed the negative affect on performance of one of those – no matter what virtual/hardware was thrown at it.

The final element of the equation will be cost. I have no idea how the cost of the EPYC-powered machines will compare with the Xeon-powered ones. I do know that the AMD processor is cheaper and offers more threads per socket, and it should require less power. That should make it a cheaper machine to run, but higher consumption of IOs per machine might increase the cost to the hosting company (Azure). I guess we’ll know soon enough when the pricing pages are updated.

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2 Replies to “What Impact on You Will AMD EPYC Processors Have?”

  1. I might be off here, but it seems like I remember choosing a CPU for a host back in the days affected your ability to migrate virtual machines. Does choosing AMD or Intel powered virtual machines have any impact down the road? If I choose AMD now am I stuck, or maybe it doesn’t matter…

    • Very good question. We will find out soon when this stuff becomes more available. Worst case, it’ll be a matter of backup/restore or do an out-of-band conversion using a JSON export, similar to my recent Azure Firewall post.

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