Category Archives: Hyper-V

Accelerated Checkpoint merging with ReFS v2 in Windows Server 2016

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Introduction

This blog post is a teaser where we show you some of the results we have seen with ReFS v2 in Windows 2016 (TPv4). In a previous blog post (Lightning Fast Fixed VHDX File Creation Speed With ReFS on Windows Server 2016) we have demonstrated the very fast VHDX file creation capabilities we got with ReFS v2. Now we look at another benefit of ReFS v2 in a Hyper-V environment, thanks to a feature or ReFS v2 called block cloning. We get accelerated checkpoint merging with ReFs v2 in Windows 2016

The Demo

For this short demo we have a virtual machine running Windows Server 2016. It resides on a CSV formatted with REFS (64K unit allocation size). Inside the virtual machine there is a second data disk. Our  VM called CheckPointReFS (64K unit allocation size) has this data volume formatted with ReFS (64K unit allocation size) and it runs on the ReFS formatted CSV. The disks in this test are fixed sized VHDX files.

On the data volumes we have about 30GB worth of ISO files. We checkpoint the VMs and then create a copy of those files on the data volume.

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We then delete this checkpoint.

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Via the events 19070 (start of a background disk merge) and 19080 (completion of a background disk merge) in the Microsoft-Windows-Hyper-V-VMMS/Admin logs we calculate the time this took: 5 seconds.

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There are moments you just have to say “WAUW”. Really this rocks and it’s amazing. So amazing I figured I made a mistake and I ran it again … 4 seconds. WOEHOE!  What where the times you saw when you last deleted a large checkpoint?

I am really looking forward to do more testing with ReFS v2 capabilities with Hyper-V on Windows 2016.

Creating a bootable VHD or VHDX from an existing one

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Creating a bootable VHD or VHDX from an existing one is a great capability to have.There are a couple of reasons why one might need or want to do this. In windows 2012 (R2) this is even a part of normal live migration operations. Storage live migration for example is nothing but the live streaming of the data of your live virtual hard disk into a new VDH/VHDX. You have multiple options when it comes to creating a bootable VHD/VHDX from an existing one and they all serve their specific purposes,which might or might not overlap.

This is great stuff to do migrations, reorganize storage, defrag your internal dynamic VHDX structure etc.  But you’re not limited to those options. When you want to convert from VHD to VHDX you’ll leverage Convert-VHDX. You can also create a new VHDX with an old one as the source with New-VHDX. Great for all kind of operations including off line migration, updates, testing on exact copies of the original disk etc. You might think it’s better to just copy the disk but for a conversion that will not work, that won’t deal with internal fragmentation which can be important for performance testing when your migrating to new storage, a new cluster & Hyper-V version and such.

Recently people asked me if this would work with their OS disk. The virtual disk that the boot from. Yes that will work. Both New-VHD and Convert-VHD will create a fully bootable new virtual disk if the source virtual disk was bootable to begin with. No problem, They have to, if you think about it. Using Convert-VHD to move from VHD to VHDX and even change the cluster sizes of the disk would be no good if the VM doesn’t boot anymore. Like wise with New-VHD.

The only thing that need some real tender loving care is when you convert a VM from generation to generation 2. The script provided to to that by John Howard (MSFT) use fully supported technologies. The script itself is not a supported product, but you’re not doing anything unsupported with it.

So all people needing to convert, defrag or move  VMs to new virtual hard disks. Do a few test to verify your assumptions and go forward. Step into that bright new future you’ve been missing out on for the past 3 years.

Windows Server 2016 TPv4 Hyper-V brings virtual machine configuration version 7

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When building a Windows Server  2016 TPv4 Hyper-V cluster this weekend I noticed that we now have a new version of the virtual machine configuration.

When we migrate (rolling cluster upgrade, move to new cluster or host, import on new cluster or host) virtual machines to  Windows Server 2016 Hyper-V from Windows Server 2012 R2, the virtual machine’s configuration file isn’t automatically upgraded. In the past it was, which blocked moving back to a previous edition of Hyper-V. Now we can do this until we manually update the virtual machine configuration version.  This block going back but it enables our new virtual machine features. Version 5.0 is the one that’s compatible with Windows Server 2012 (R2) Windows Server 2016. Version 6.2 was what we had in TPv3 and could only run on Windows Server 2016. Windows Server 2016 TPv4 Hyper-V brings virtual machine configuration version 7.

When you have virtual machines that come from  Technical Preview v3 and you had updated the virtual machine configuration of your virtual machines or created brand new ones these would be at version 6.2. Since I do not consider it wise to keep testing these on a version of a previous preview I updated them all to version 7.

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The code below grabs all VMs on all cluster nodes (even the none clustered VMs), shuts them down, updates the configuration version and starts them again. It’s just a quick example.

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Now do NOT do this to virtual machines with configuration version 5 that you might want to move back / import to a Windows Server 2012 R2 Hyper-V host. But if you know you’ll be testing with the new features, have a blast, like me here on the TPv4 lab cluster.

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I’m still looking for the features version 7.0 enables, probably nested virtualization is one of those features I’m guessing. Happy testing!

NIC Firmware/Driver Updates Reset Your RSS/VMQ optimizations

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When optimizing your RSS/VMQ settings for maximum performance you’ll normally (I hope) do this in PowerShell. Save that script with some comments on why you configure it that way and make it part of your Hyper-V host deployment scripts

Why? Automation is king but you’ll need it again for sure. Why? Well there is this “tendency” that NIC firmware/driver updates reset your RSS/VMQ optimizations back to their defaults.That’s a bit of a bummer if you have to redo all the work instead of having a script ready to go. I have seen many a deployment where the configuration was missing after firmware/driver upgrades so please, check!

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Figure: Where has my optimized configuration gone after a driver/firmware upgrade?

The good news is this isn’t a show stopper issue as things will keep working, but without your optimizations and with VMQ, depending on your NIC team setup for the vSwitch issues might occur. When doing NIC teaming for your virtual switch it’s important to get it right.  With switch dependent teaming (LACP/Static) the NICs in the team need to use overlapping processor sets (Min Queues). When doing switch independent teaming the NICs in the team need to use non-overlapping processor sets. So you need to configure each NIC in your team to use the different processors (Sum of Queues).

On top of that you might want to / should separate RSS/VMQ cores from each other. SMB Direct for CSV/LM will also help achieve this as there we leverage CPU offloading to the NIC.