Today, I’ll talk about a thing that any sysadmin running Hyper-V VMs does (or still dreams about) while managing infrastructure resources: hot modifying assigned to VM memory amount. I’ll discuss not only the feature itself but also how it works on different OS and its impact on the environment stability.

All of us keep an eye on resource consumption within our environments. If a VM needs extra RAM to have the job done, we provide it with some, right? And, we usually run many VMs on our servers each with own purpose and configuration. That’s, actually, why changing the amount of assigned to a VM memory without rebooting it may come in handy. Also, many guys run some parts of their environments on Windows while having other parts run on something from Linux family. Looks pretty hectic in terms of management, doesn’t it?

In today’s topic, I’d like to talk about the Meltdown and Spectre vulnerabilities. But not about the harm they cause, this has been covered widely in numerous articles, but how Microsoft patches intended to protect you from the vulnerabilities, affect (if they do) the hardware performance. Before we take a deep dive into the tests and numbers, let me tell a few words about Meltdown and Spectre and outline the testing scope to make sure we speak one language.

For that matter, I’ll create a file server of two types: “File server for general use” and Scale-Out File Server. For the latter, I’ll have two scenarios: VMs running and off. After that, I’m gonna evaluate the deduplication ratio using a free tool – StarWind Deduplication Analyzer. And finally, run data deduplication using the Windows Server 2016 Data Deduplication feature. We also need our storage shared, so for this purpose, I’ve decided on StarWind Virtual SAN Free.

How does it work?

Being triggered, the Node Fairness service determines the current workload on the cluster hosts. If needed, it automatically migrates VMs to the less loaded host.

After the start, the cluster service checks the host for two factors:

• If the average host CPU load exceeds the tolerated threshold
• If the average host memory utilization is higher than the tolerated threshold

In case either of these criteria is met, the VM gets live migrated to the less loaded host. Neither guest system nor services do experience any downtime.

So, we all know about Microsoft’s Storage Spaces Direct (S2D to put it simple) by now. It’s the feature introduced in Microsoft Server 2016 (Datacenter Edition) that pools together server’s storage allowing to build…that’s right: highly available and easily scalable software-defined storage systems. In this article, I’m gonna talk about not as much about its fault-tolerance characteristics themselves, but some hands-on experience, namely: how to replace a failed disk.

Microsoft operating systems and server applications are becoming increasingly dependent on proper time synchronization. A skewed system clock can affect your ability to log on, can cause problems with mail flow in Exchange, and be the source of a great many difficult-to-locate problems. To compound matters, the default method of handling time synchronization within a Windows network isn’t exactly reliable or even predictable. If a Hyper-V host’s clock becomes out of sync, it usually affects all of its virtual machines, sometimes catastrophically. Fortunately, it doesn’t take much work to get everything in sync.