Windows Server on ARM: what does it mean?

Qualcomm Centriq ARM server

The demonstration of a version of Windows Server running on ARM-based servers came as a shock to many, especially as this is something that Microsoft has expressly ruled out in the past. But look closely and there is no suggestion as yet that this will lead to commercial availability of such products.

This first public demonstration of Windows Server running on ARM-based systems came at the Open Compute Project (OCP) Summit 2017 in Santa Clara. It was conducted by chipmaker Qualcomm, using its Centriq 2400 platform that boasts up to 48 cores based on ARM’s 64-bit ARMv8 architecture.

Microsoft is also working with at least one other chipmaker, Cavium, which trumpeted its own involvement in a statement saying it was “collaborating with Microsoft on evaluating and enabling a variety of cloud workloads running on Cavium’s flagship ThunderX2 ARMv8-A Data Center processor for the Microsoft Azure cloud platform”.

The key phrase here is “for the Microsoft Azure cloud platform”. This version of Windows Server, and the systems it is running on, seem to be part of an evaluation by Microsoft to see how well ARM-based servers can run some of its cloud services operated from its network of data centres.

ARM has been taking aim at the server market for at least the past five years, at least as far back as the launch of its 64-bit ARMv8 architecture. The proposition is that ARM cores are less complex and consume less energy than rival architectures, such as Intel’s x86 and IBM’s Power processors.

[For more on this, see my article on IDG Connect: No ARM in a bit of server market competition]

However, expert opinion has so far been that the economics of this would only really make sense for hyper-scale environments – typically meaning the large cloud service and internet companies such as Google, Facebook, AWS, and Microsoft, which operate tens of thousands or even millions of server nodes. These are the companies for whose requirements the OCP was started in the first place.

In a post on Microsoft’s Azure blog, Distinguished Engineer Leendert van Doorn confirmed that the ARM servers are currently for Microsoft’s internal use only:

“We have been working closely with multiple ARM server suppliers, including Qualcomm and Cavium, to optimize their silicon for our use. We have been running evaluations side by side with our production workloads and what we see is quite compelling.”

What this may mean is that Microsoft could be planning to migrate some of its cloud services over to ARM-based infrastructure at some point in the future. How worried should Intel be about this move?

The reality is that x86 systems are not going to go away, for the simple reason that the virtual machine workloads that Microsoft customers have hosted on Azure require an x86 server to run on: pretty much every enterprise in the world is run on x86 servers, and these customers expect any public cloud infrastructure-as-a-service (IaaS) to do the same for compatibility reasons.

Again, Microsoft confirms this in the blog:

“One of the biggest hurdles to enable ARM servers is the software. Rather than trying to port every one of our many software components, we looked at where ARM servers are applicable and where they provide value to us. We found that they provide the most value for our cloud services, specifically our internal cloud applications such as search and indexing, storage, databases, big data and machine learning.”

“To enable these cloud services, we’ve ported a version of Windows Server, for our internal use only, to run on ARM architecture. We have ported language runtime systems and middleware components, and we have ported and evaluated applications, often running these workloads side-by-side with production workloads.”

So, don’t expect to see ARM-based Windows Servers anywhere except in hyper-scale cloud data centres for now. Of course, where Microsoft leads, others may follow, but the huge installed base of Intel-based servers out there means that the average company is not going to be buying ARM servers anytime soon.