I try to avoid writing blog posts that I like to call “hot takes”—quick crappy opinions on the news of the day, but this is a topic I feel particularly strongly about. I’m not sure how many of you were using Microsoft’s Azure Hadoop offering HDInsight, when it debuted in the 2012-13 timeframe, but it had a unique characteristic. Unlike virtually every other Hadoop offering at the time (and this was a hot era for Hadoop) HDInsight ran on Windows Server. That meant all the assorted utilities in and around Hadoop were always trailing what was current on Linux. It also meant that when you had issues, and you searched for help in various online forums, you were always challenged because you got weird error messages, and your cluster used oddball file pathing because Windows. Since 2013, Microsoft has gotten a new CEO, the stock price has shot way up, and the company has embraced open source software. SQL Server is on Linux now, which leads me to my next points.
Ever since SQL Server Helsinki debuted in Docker, I’ve seen the benefit of using containers with databases. When SQL Server started supporting Kubernetes, I really saw the benefit and quickly embraced this, by writing and presenting on the topic, and evangelizing all the benefits of the Kubernetes platform (of which there are many). Before I start my rant, remember in a container platform, there is only one copy of the base operating system on a given host. Your container contains the libraries and binaries it needs but shares a kernel with the host operating system. This means the base operating system of the host must be the same as that of the container.
Much like Hadoop, Kubernetes was built from the ground up as a Linux based platform. When Google built the Borg cluster management system that eventually became Kubernetes, it was reportedly built on a custom build of OpenBSD. This means there a lot of assumptions about the way things work in Linux that are built into Kubernetes. While, I know I’ve heard a reasonable amount of community demand for Windows containers (clearly enough that Microsoft has made an effort to build support both into Windows Server and Azure Kubernetes Services), I can’t help but feel this is not a good long term plan.
When dealing with open source software, it’s good to be on a platform that is widely utilized. When you are searching for help on forums, or looking for the latest patch, the platform that is the most widely utilized. Another example I like to use for this, is Oracle on Windows, which I supported in a past life. Since Oracle was most commonly run on Linux/UNIX, patches for Windows were always days and weeks behind. While, I appreciate the effort of the Windows team to build container and Kubernetes support into the platform, Microsoft is going to be the only support/patching path for Kubernetes on Windows, which hampers one of the key benefits of OSS, rapid fixes.
There’s another elephant that’s in the room—in this scenario, Linux is free as in beer, and you will have to license (pay for) your Windows nodes. If you are running a supported version of Linux like Red Hat (now presented by IBM), you will pay about the same cost as Windows Server licensing, but in most cases organizations running Kubernetes are doing it on a free version of the operating system.
I don’t mean to slight anything Microsoft is doing (note: I’m a shareholder and current a contractor at MS), but I feel as though if you are implementing Kubernetes on Windows, you are likely doing containers wrong. With .NET Core and SQL Server being available on Linux there are few reasons to tie your development to the Windows platform. System administration reasons like domain authentication and group policy support make some sense to me, however I can’t help but think this feels like Hadoop on Windows. Also, the lack of community support can’t be overemphasized–this is a big deal, especially on a not fully mature platform like Kubernetes. By the way, Microsoft stopped offering HDInsight on Windows sometime in 2014-15, just saying.