This post addresses Hyper-V live migration – the topic which any admin faces with at some point. In my salad days of working as an admin, Hyper-V live migration was a saving grace, so I decided to write an article about it. In this article, I want to cover some live migration and migration wizard settings that ensure maximum performance of this process.
Some time ago, I wrote an article about backup storage media. Today, I’d like to talk about secondary storage. Before I move on, I want to clarify what I mean by “secondary storage” here, just to make sure that we are on the same page. Secondary storage is the storage where the actively used data resides. It can be both some local storage like SAN or NAS, or some public cloud hot tier. Well, it’s absolutely true that you can use disk arrays too, but let’s think of them today just as NAS-like servers packed with many disks, ok? That’s entirely up to you “which side you are on”, and there’s no “one-size-fits-all” solution. NAS, SAN, and public cloud storage… Whatever secondary storage you choose, it has own pros and cons. I discuss them in this article.
How to save disk space in Clustered File Servers on Windows Server 2016 using Data Deduplication feature
So we all know about the benefits you get with data deduplication technology. Long story short, it minimizes server application’s storage consumption by reducing the amount of redundant data stored on the disk. As the result, you should get more space for your VMs and applications. How does it work for a file server? Well, that’s what I’m gonna test here.
For quite a long time, System Center Virtual Machine Manager (SCVMM) has a feature called Dynamic Optimization. Its main goal is to automatically rebalance VMs between the participating cluster nodes in case the placement is unequal. Now, this feature has partially became available in Windows Server 2016 in the form of Node Fairness. It balances the workloads among the hosts in a Hyper-V Failover Cluster and automatically live migrates guests from an overloaded node to a less busy one with zero downtime.
Node Fairness goes embedded in Windows Server 2016 and is intended for deployments without SCVMM. SCVMM Dynamic Optimization delivers more versatile functionality than Node Fairness. Regarding this fact, Dynamic Optimization is recommended for balancing workloads among the cluster hosts. However, to use this feature, you need an additional license from the main operating system.
Now that we know what Node Fairness is, let’s take a look at how this service works.
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.
Pick a Computer to Server as the Authoritative Internal Time Source
The first thing you want to do is decide what machine you want to serve as the authority of time within your domain. In most cases, I choose the domain controller that holds the PDC emulator role. According to Microsoft’s documentation, that’s supposed to be the highest authority on the matter anyway, although it doesn’t seem to work out that way in practice. The machine that you choose will be regularly consulting Internet sources, so if you’re in a high-security facility, you might consider delegating this role to a different computer. You could have multiple machines serving as authoritative time sources, but more than one per site generally is unnecessary. You could also have one machine pull external time and have your PDC emulator use that as its source while still serving as the authoritative server for the rest of the computers in your domain.
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