Category Archives: Hyper-V

Golden Nuggets: Windows Server 2012 R2 Failover Cluster CSV Placement Policy

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Some enhancements only become truly evident to people when they see them in action. For many features this means something need to go wrong before they kick in. Others are more visible during normal operations. This is the case with the CSV enhancements in Windows Server 2012 R2 Failover Clustering.

One golden nugget here is the CSV placement policy (which really shines in combination with SOFS/Storage Spaces). This will spread ownership of the CSV amongst the cluster nodes to ensure a balanced distribution. In a failover cluster, one node is the “coordinator node” (owner) for a CSV. The coordinator node owns the physical disk resource that is associated with a logical unit (LUN). All I/O operations for the File System on that LUN are are through the coordinator node. In previous versions there is no automatic rebalancing of coordinator node assignment. This means that all LUNs could potentially be owned by the same node. In storage spaces & SOFS scenarios becomes even more important.

The benefits

  • It helps all nodes carry their share of the workload as it load balances the disk I/O.
  • Failovers of CSV owners are potentially quicker and more predictable/consistent as an even distribution ensures that no one node owns a disproportionate number of CSVs.
  • When losing storage access the number of CSVs that are in redirected mode is potentially less as they are evenly distributed. In an unbalanced cluster it could be for all of them in a worse case scenario.
  • When using SOFS with Storage Spaces it makes sure the Storage Spaces Ownership is distributed fairly.

When does it happen

  • Each time a node leaves or joins the cluster. This means you don’t need to intervene manually or via PowerShell to get an even distribution. This goes for both exiting nodes as when adding a new node. The new node will get a CSV assigned if there is any on surplus on one of the existing nodes.
  • The process also works when you start a failover cluster when it has shut down.

When customers see this in action (it’s most obvious when then add a node as then they are normally watching) they generally smile as the cluster does it job getting  the best possible results out of their hardware.

Hot add/remove of network adapters and enabling device naming in Windows Server Hyper-V

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One of the cool new features in Window Server vNext Hyper-V (in Technical Preview at the moment of writing) is that you gain the ability to hot add and remove NICs.  That might sound not to important to the non initiated in the fine art of virtualization & clouds. But it is. You see anything you can do to a VM configuration wise that does not require downtime is good. That’s what helps shift the needle of high availability to that holey grail of continuous availability.

On top of that the names of the network adapters are now exposed to the guest. Which is also great. It’s become lot easier to automate the VM network configuration.

Hot adding NICs can be done via the GUI and PoSh.

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But naming the network adapter seems a PowerShell only game for now (nothing hard, no sweat). This can be done during creation of the network adapter. Here I add a NIC to VM RAGNAR connected to the ISCSI-GUEST switch & named ISCSI.

Add-VMNetworkAdapter –VMName RAGNAR –SwitchName ISCSI-GUEST –Name ISCSI

Now I want this name to be reflected into the VM’s NCI configuration properties. This is done by enabling device naming. You can do this via the GUI or PoSh.

Set-VMNetworkAdapter –VMName RAGNAR –Name ISCSI –Devicenaming On

That’s it.

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So now let’s play with our existing network adapter “Network Adapter” which connects our Hyper-V guests to the LAN via the HYPER-V-GUESTS switch? Can you rename it?  Yes, you can. In PoSh run this:

Rename-VMNetworkAdapter –VMName RAGNAR –Name “Network Adapter” –NewName “LAN”

And that’s it. If you refresh the setting of your VM or reopen it you’ll see the name change.

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The one thing that I see in the Tech Preview is that I need to reboot the VM to see the Name change reflected inside the VM in the NIC configuration under advance properties, called “Hyper-V Network Adapter Name”. Existing one show their old name and new one are empty until then.

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Two important characteristics to note about enabling device naming

You notice that one can edit this field in NIC configuration of the VM but it doesn’t move up the stack into the settings of the VM. Security wise this seems logical to me and it’s not intended to work. It’s a GUI limitation that the field cannot be disabled for editing but no one can try and  be “funny” by renaming the ethernet adapter in the VMs settings via the guest Winking smile

Do note that this is not exactly the same a Consistent Device Naming in Windows 2012 or later. It’s not reflected in the name of the NIC in the GUI, these are still Ethernet, Ethernet 2, … Enable device naming is mainly meant to enable identifying the adapter assigned to the VM inside the VM, mainly for automation. You can name the NIC in the Guest whatever works best for you and you’ll never lose the correlations between the Network adapter in your VM settings and the Hyper-V Network Adapter name in the NIC configuration properties. In that respect is a bit more solid/permanent even if some one found it funny to rename all vNICs to random names you’re still OK with this feature.

That’s it off, you go! Download the Technical Preview bits from MSDN, start exploring and learning. Knowledge is seldom a bad thing Winking smile

The Hyper V Amigos Showcast Episode 6: Storage Spaces

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Everybody is very busy and I’m a bit tires but here’s the 6th episode of the Hyper-V Amigos show cast. In this episode we get to play a bit with storage spaces in Carsten’s lab.

As always we had a lot of fun doing so and thanks to Carsten Rachfahl and the assistance of Kerstin (his charming wife, also an MVP, in Office 365) we could simulate hardware failures & film them for you!

 

Carsten & I discuss several scenarios and what’s happening during failovers. Carsten is assisting customers with this a lot so he has some of the most varied experience with storage spaces and SOFS out there!  Interesting stuff and for people who haven’t even looked at Windows Server 2012 or later yet a wake up call to start as the world is not limited to what we once knew. It’s not your daddy’s Windows anymore Winking smile

I hope you enjoy it and we’re already planning for the next one!

Hot Add & Remove Static Memory in a Hyper-V vNext Virtual Machine

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One of the very nice and handy new capabilities in Windows Server vNext Hyper-V (Windows Server 2015 or Windows Server 10?) is the fact that you can now hot add or remove memory from a virtual machine with a fixed amount of memory. Another step towards continuous availability.

Here’s a test virtual machine RAGNAR running the Technology Preview bits on my test cluster. As you can see it has 1024MB of fixed memory. And Dynamic memory is not enabled.

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I can simply adjust this upward by typing in the value and clicking “Apply”

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and downwards in the same way

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Cool huh!

On top of this to make sure you’re not adding memory needlessly when someone says they need more memory for their VM you can see the memory demand now in the GUI. Both in Hyper-V Manager and in the Failover Clustering GUI.

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The technical preview of Windows vNext is looking good even in this early stage and I have no doubt it’s only going to get better Open-mouthed smile.

Some things to note

  • It’s configurable via PowerShell so you can start dreaming of script to query memory assignment & demand and use that output to redistribute memory available on the host amongst the VMs …

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  • Both Hyper-V host and guest have to run vNext (Technical Preview)
  • The guest has to be a generation 2 VM
  • It’s still virtualization technology and not magic, so if you try to assign more memory than available you’ll get a warning Winking smile

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