Archive for the ‘Hyper-V’ Tag

A short note about AD detached clusters in Windows Server 2012 R2   Leave a comment

Yesterday Microsoft posted an article about a new way to deploy clusters in Windows Server 2012 R2 called Active Directory Detached Clusters. As the name implies this type of cluster do not rely on your AD in order to operate, instead using DNS for the Computer Name Objects and the Virtual Computer Objects.

This is great news as I’ve had several clusters acting up due to the domain controller not being reachable but there is one important caveat with this mode:

The intra-cluster communication would continue to use Kerberos for authentication, however, the authentication of the CNO would be done using NT LM authentication. Thus, you need to remember that for all Cluster roles that need Kerberos Authentication use of AD-detached cluster is not recommended.

This means that Live Migration isn’t supported for a Hyper-V cluster, only Quick Migration.

More information here.

Posted 25 March, 2014 by martinnr5 in Documentation, Operating system, Technical

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A gathering of links, part 3   Leave a comment

Sorry for the lack of content. I have something I can write about, I think, but work is getting in the way.

For now, a gathering of links instead.

Cripes! I need to do these more often, this took me forever.

If you find these useful, please rate this blog post or leave a comment. There’s really no need for me to spend my morning doing this if no-one’s going to read it. 🙂

Real world scenario issues with VMQ   Leave a comment

Last week Microsoft published part 1 in an article series about VMQ, detailing how VMQ works and trying to clear up some misconceptions about the technology.

It’s well worth the read but the main reason I mention it is because a colleague of mine ran into an issue that’s very much related to VMQ.

The customer is a large hosting provider and they experienced poor network performance when doing backups and live migrations over their 10 Gbit infrastructure. Very important to know though is that they use a virtual switch in Hyper-V to provide vNICs  for backup and LM.

As the Microsofts article states, you won’t get 10 Gbit out of a Hyper-V switch:

Many people have reported that with the creation of a vSwitch they experience a drop in networking traffic drop from line rate on a 10Gbps card to ~3.5Gbps. This is by design. With RSS you have the benefit of using multiple queues for a single host so you can interrupt multiple processors. The downside of VMQ is that the host and every guest on that system is now limited to a single queue and therefore one CPU to do their network processing in the host. On server-grade systems today, about 3.5Gbps is amount of traffic a single core can handle.

Their bandwidth was somewhat lower, around 3 Gbps, but that’s most likely due to having older hardware.

I’m not sure how they’re going to resolve this but my suggestion was to use separate, physical, NICs for backup and, if needed, for LM.

As I don’t have enough information about how they’ve designed their Hyper-V environment I’m not sure if they’ve scaled up or out. If they scale out, bandwidth for LM should be less of an issue as fewer VMs lives on each host but at a certain point you’re still going to need bandwidth (unless you plan on patching your hosts continuously).

The takeaway from this is that when designing high-end environments, it pays to know the nuts and bolts of the technology you’re using.

Posted 20 September, 2013 by martinnr5 in FYI, Technical

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Some unusual behaviour from Best Practice Analyzer   Leave a comment

A customer of mine recently ran a Best Practices Analyzer scan on his new Hyper-V 2012 setup in order to make sure everything was by the book.

Besides a couple of minor issues one warning stood out to him: “The memory configuration for one or more virtual machines might require the use of Smart Paging if the virtual machine is rebooted, and the specified location for the Smart Paging file is the system disk of the server running Hyper-V.”

He was sure there was no way the Smart Paging file wasn’t located on his CSV’s and decided to check. Sure enough, it’s located on a CSV:

Smart Paging file location

The only hit I get when searching for this exact error message is a TechNet Wiki article telling you not to store the Smart Paging file on the system disk. Thanks, I guess. 🙂

We’ve come to the conclusion that this is a bug in the BPA as it complains on all his VMs, despite them all being correctly configured.

Has any one of you reading this encountered this behaviour?

Posted 17 September, 2013 by martinnr5 in FYI, Technical, Tools

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“Clipboard” disks in Hyper-V   Leave a comment

With Windows Server 2012 R2 we’ll be getting a complete RDP experience when connecting to a VM through Hyper-V Manager, Failover Cluster Manager or VMM which means that we’ll get an easy way to copy content to a VM that’s otherwise isolated from a network.

There are still a couple of reasons why you’d want an alternative though and I’d like to present mine.

I’m certain that I’m not the only one looking for a solution to this problem and I’m equally sure that I’m not the only one who thought that hot-adding and removing disks to the SCSI-controller in a VM and then mounting and unmounting the VHD/VHDX to the host is an interesting way to do it.

I’d also be very surprised if I’m the only one who scripted this to some degree but as I wanted to write some PowerShell I haven’t checked if anyone else has done this.

So, here’s my version of a script for managing what I call “clipboard” disks. I’m not that good with PowerShell so it’s rather crude and although I’ve added what I think is enough for a version 1.0 there’s still lots of room for improvement so feel free to provide feedback in the comments.

Download from SkyDrive:

 Martin Edelius, 2013-07-12. Find me at

 Allows you to attach and remove a VHDX to a running VM as well as to the host the VHDX is located on in a controlled manner.

 The script requires you to create a base clipboard VHDX, formatted and ready to use, located in an appropriate place on the Hyper-V host.

 If the VM you select to connect a VHDX to doesn't have a unique clipboard disk the script will create one based on the base clipboard disk.

 The script toggles the clipboard disk between being attached to the VM and to the host until you manually exit the loop.

 The script also provides options for removing the clipboard disk from all VMs and also to unmount them all from the host.

 In order to locate the clipboard disk the script uses location 63 on SCSI-controller 0 of the VM which means that A) you need a SCSI-controller and B) that location has to be empty.
 PS> ClipboardDisk.ps1
 This starts the script which from here on is interactive. The script doesn't accept any parameters.
 You must be running as a user that has permissions to attach a VHDX to a VM and also permissions to mount a VHDX to the host.

 Feel free to modify and distribute this script to your hearts content but if you do any major modifications I want you to post a comment to this post: with a link back to your modified script so that others may benefit from it.

 Finally; you're using this completely on your own risk, I take no responsibility for any damage this script may do. If something breaks, you own both parts.

# Path to the base clipboard disk that is used for new, unique clipboard disks
# Do not forget the trailing '\'!
$BaseClipboardDiskPath = "C:\VHD\Clipboards\";

# Name of the base clipboard disk that is used for new, unique clipboard disks
$BaseClipboardDiskName = "Clipboard - base.vhdx";


# Select action
Write-Host("Select option:`n1. Toggle clipboard disk for VM (default)`n2. Unmount all disks from host`n3. Disconnect clipboard disk from all VMs");
$Action = Read-Host("[Enter = default]");

# Set default behaviour
if($Action.Length -eq 0)
    $Action = 1;

    1 # Toggle clipboard disk
        # Loop through VMs and list their names and corresponding numbers
        $VmInfo = @{};

        $VMs = Get-VM;

        # Make sure that we actually have any VMs to list
        if($VMs.Length -eq 0)
            Write-Host("`nCouldn't find any VMs, do you have correct permissions to list them?`n");
            Write-Host(" ");   # Just to introduce a newline, for readability's sake.
            $VMidx = 1;
            foreach($VM in $VMs)
                Write-Host($VMidx.ToString() + ": " + $VM.Name);
                $VmInfo.Add($VMidx++, $VM.Name);

            # Grab the index of the VM we want to attach a clipboard disk to
                $VMidx = Read-Host("Choose VM (1 - " + $VmInfo.Count + ")");
            while($VMidx.Length -le 0 -and $VMidx -le 0);

            # Grab the name of the VM from the info hashtable
            $VMname = $VmInfo.Get_Item([int]$VMidx);

            # Do we have a unique clipboard disk for this VM?
            $VMDiskPath = "$BaseClipboardDiskPath$VMname.VHDX";

            if(!(Test-Path $VMDiskPath))
                # Create new clipboard disk
                Write-Host("`nCreating unique clipboard disk: $VMDiskPath");
                Copy-Item "$BaseClipboardDiskPath$BaseClipboardDiskName" -Destination $VMDiskPath;
                Write-Host("`nUnique clipboard disk exists: $VMDiskPath");

            # This runs in a loop that only exits when the user enters the letter 'q'
                # Grab all disks attached to this VM
                $VMHDAttached = $false;
                $VMHardDisks = Get-VM -Name $VMName | Get-VMHardDiskDrive

                # We need a way to identify the clipboard disk so it always attaches to SCSI-controller 0, position 63
                foreach($VMHardDisk in $VMHardDisks)
                    if($VMHardDisk.ControllerType -eq "SCSI" -and $VMHardDisk.ControllerNumber -eq 0 -and $VMHardDisk.ControllerLocation -eq 63)
                        $VMHDAttached = $true;

                # Did we find one at our designated clipboard position?
                    # Disk is attached so lets remove it and then mount it to our host
                    Remove-VMHardDiskDrive -ControllerLocation 63 -ControllerNumber 0 -ControllerType SCSI -VMName $VMName;
                    Write-Host("`nDisk removed from VM!");
                    Mount-VHD $VMDiskPath;
                    Write-Host("Disk mounted to host!");
                    Write-Host(" ");   # Need to introduce a newline, for readability's sake.
                    # Unmount disk from host and then attach to VM
                    if((Get-VHD -Path $VMDiskPath).Attached -eq $true)
                        # Only dismount if it's attached to the host to begin with. Duh.
                        Dismount-VHD $VMDiskPath;
                        Write-Host("Disk unmounted from host!");
                    Add-VMHardDiskDrive -VMName $VMName -ControllerLocation 63 -ControllerNumber 0 -ControllerType SCSI -Path $VMDiskPath
                    Write-Host("Disk attached to VM!");

                $subAction = Read-Host("'Q' to quit loop, [Enter] to toggle");
            while($subAction.ToUpper() -ne 'Q');

    2 # Unmount all VHDs from host
        $VHDs = Get-VHD "$BaseClipboardDiskPath*.VHDX";

        foreach($VHD in $VHDs)
            if($VHD.Attached -eq $true)
                # Only dismount if it's attached to the host to begin with. Duh.
                Dismount-VHD $VHD.Path;
                Write-Host($VHD.Path +" unmounted from host!");


    3 # Disconnect clipboard VHD from all VMs
        $VMs = Get-VM;

        foreach($VM in $VMs)
            $VMHardDisks = $VM| Get-VMHardDiskDrive;

            # We need a way to identify the clipboard disk so it always attaches to SCSI-controller 0, position 63
            foreach($VMHardDisk in $VMHardDisks)
                if($VMHardDisk.ControllerType -eq "SCSI" -and $VMHardDisk.ControllerNumber -eq 0 -and $VMHardDisk.ControllerLocation -eq 63)
                    Remove-VMHardDiskDrive $VMHardDisk;
                    Write-Host("`nDisk disconnected from VM " + $VM.Name +"!");

Posted 12 July, 2013 by martinnr5 in Technical, Tools

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A gathering of links, part 1   Leave a comment

As I’ve mentioned previously, I’m not a big fan of regurgitating content from other blogs as I gather that you already subscribe to posts by Microsoft in particular but also posts on other blogs of note.

Still, this blog is one way of providing my colleagues with ongoing information about Hyper-V, Windows Server and System Center (or at least those components I find interesting) which means that I from time to time will post a round-up of links that I’ve collected.

There will be no real order or grouping to these links, at least not for now.

All hosts receive a zero rating when you try to place the VM on a Hyper-V cluster in Virtual Machine Manager – If you have a setup where you use VLAN isolation on one logical network and no isolation on another you could happen upon this known issue in VMM 2012 SP1.

Ben Armstrong posts about a nifty little trick allowing you to set your VMs resolution to something else than the standard ones. Useful when you run client Hyper-V.

Neela Syam Kolli, Program Manager for DPM, posted a really interesting article called “How to plan for protecting VMs in private cloud deployments?” There’s quite a bit of useful information in this post but also some solid advice on how to plan your VM to CSV ratio, a question that I’ve been asked by customers and colleagues alike so let me go into a bit more detail on this.

From the article (my emphasis):

Whenever a snapshot is taken on a VM, snapshot is triggered on the whole CSV volume. As you may know, snapshot means that the data content at that point in time are preserved till the lifetime of the snapshot. DPM keeps snapshot on the volume on PS till the backup data transfer is complete. Once the backup data transfer is done, DPM removes that snapshot. In order to keep the content alive, any subsequent writes to that snapshot will cause volsnap to read old content, write to a new location and write the new location to the target location. For ex., if block 10 is being written to a volume where there is a live snapshot, VolSnap will read current block 10 and write it to a new location and write new content to the 10th block. This means that as long as the snapshot is active, each write will lead to one read and two writes. This kind of operation is called Copy On Write (COW). Even though the snapshot is taken on a VM, actual snapshot is happening on whole volume. So, all VMs that are residing in that CSV will have the IO penalty due to COW. So, it is advisable to have as less number of CSVs as possible to reduce the impact of backup of this VM on other VMs.  Also, as a VM snapshot will include snapshot across all CSVs that has this VM’s VHDs, the less the number of CSVs used for a VM the better in terms of backup performance.

Despite the language being a bit on the rough side the way I interpret this is that it’s preferable to have as few VMs as possible per CSV due to the COW impact on all VHDs on a CSV. Additionally, keep all your VHDs for a VM on the same CSV as all CSVs that host a VHD for the VM you’re protecting will suffer the COW performance hit.

The response I’ve gotten from Microsoft and the community regarding number of VMs per CSV is “as many as possible until your storage can’t handle the load” which is perfectly logical but also very vague. If you use DPM to protect your VMs you now have a bit more to lean on when sizing the environment. There is of course a reason that we use CSV and not a 1:1 ratio of volumes to VHDs so don’t go overboard with this recommendation.

Moving on.

This one is pretty hardcore but interesting none the less; How to live debug a VM in Hyper-V. If nothing else, it shows that there’s still a use for COM-ports in a VM.

vNiklas is as always blogging relentlessly about how to use PowerShell for pretty much everything in life. This one is about how to re-size a VHDX while it’s still online in the VM.

If you want to know more about how NIC teaming in Windows Server 2012 works then Didier van Hoye takes a look at how Live Migration uses various configurations of the NIC teaming feature. A very informative post with a surprising result!

Another post from Ben Armstrong, this time he does some troubleshooting when his VMs hover longer than expected at 2 % when starting up. Turns out that it’s due to a name resolution issue.

Microsoft and Cisco have produced a white paper on the new Cisco N1000V Hyper-V switch extension. It’s not very technical, although informative if you need to know a little bit more about how the N100V and the Hyper-V switch relate to each other.

The Hyper-V Management Pack Extensions 2012 for System Center Operations Manager 2012/2012 SP1 gives you even more options when monitoring Hyper-V with SCOM.

I mentioned that the post about how to live debug a VM was pretty hardcore but I’d like to revise that statement. Compared to this document called “Hypervisor Top-Level Functional Specification 3.0a: Windows Server 2012” that post is as hardcore as non-fat milk. Let me quote a select piece of text from the specification:

The guest reads CPUID leaf 0x40000000 to determine the maximum hypervisor CPUID leaf (returned in register EAX) and CPUID leaf 0x40000001 to determine the interface signature (returned in register EAX). It verifies that the maximum leaf value is at least 0x40000005 and that the interface signature is equal to “Hv#1”. This signature implies that HV_X64_MSR_GUEST_OS_ID, HV_X64_MSR_HYPERCALL and HV_X64_MSR_VP_INDEX are implemented.

My thoughts exactly! And the specification is 418 pages long so it should last you all through your vacation.

Finally (as I’m out of time and starting to get to stuff that’s a bit old), Peter Noorderijk writes about problems using Broadcom or Emulex 10 Gbit NICs. They resolved the issue by adding Intel NICs but another workaround is to turn off checksum offloading. Updated Emulex and Broadcom drives should be expected.

TechEd Europe 2013 – Virtual Networking   Leave a comment

This post is going to be the toughest one to write as virtual networking, called Hyper-V Networking by Microsoft,  is something that I haven’t had a lot of time to work with. It’s clear that Microsoft are heavily invested in Software Defined Networking (SDN) as quite a bit of work has been done in the R2 releases of Windows Server 2012 and System Center VMM 2012.

An overall theme to Microsoft’s work with SDN (and 2012 R2 in general, for that matter) is that of the three clouds; the Private Cloud, the Service Provider Cloud and Azure. They all need to work in harmony, requiring as little effort from the customer as possible to get up and running.

If we start with Windows Server 2012 R2 there’s a new teaming mode called “Dynamic” that chops up the network flow into what Microsoft calls flowlets in order to be able to distribute the load of one continuous flow over multiple team members.

Hyper-V Networking (HNV) is now supported on a network team.

NVGRE, the technique used in Windows Server to implement network virtualization, can be offloaded to network cards with this feature. VMQ in combination with NVGRE will only work on NICs with the NVGRE task offload capability.

HNV is now a more integral part of a Hyper-V virtual switch which allows third-party extensions to see traffic flow from both consumer addresses (CA) as well as provider addresses (PA). HNV now also dynamically learns about new addresses in CA which means that 2012 R2 supports both DHCP servers as well as guest clusters on a virtualized network.

On that note it’s worth mentioning that the basic version of Cisco’s extension of the Hyper-V switch, called 1000V, is completely free to download and use – essentially turning your Hyper-V switch into a Cisco switch.

The Hyper-V switch has improved ACL and can now be set on port as well as on IP. In addition to this it’s also stateful.

A virtual machine can now use RSS inside the actual VM. This is called vRSS.

Microsoft was keen to point out that there had been a lot of work done in order to make SDN not only perform better but als easier to troubleshoot. There’s a new Powershell cmdlet called TestNetConnection that is ping, traceroute and nslookup all rolled into one and 2012 R2 allows you to ping a PA by using “ping -p”

In addition to this there’s a new Powershell cmdlet that allows you to test connectivity between VMs on the CA space.

2012 R2 boasts a replacement for the tried and true NetMon, called Message Analyzer. This new tool allows you, among a lot of other things, to in near real time monitor network traffic on a remote host.

There’s a built-in multi-tenant gateway between CA and PA in 2012 R2 that should be able to scale up to 100 tenants. IPAM in Windows Server 2012 R2 can now handle guest networks and can be integrated with VMM 2012 R2.

Continuing on with VMM 2012 R2 there is now support for managing top-of-rack switches from within VMM through the OMI standard. So far only Arista has announced support for this but other hardware vendors should follow. Look for the Microsoft certification logo.

This allows for a number of interesting features in VMM, one that was demonstrated was the ability to inspect the configuration of a switch and if needed remedy it from within VMM.

I’m not sure how many of my customers that can use all these features, and SDN in particular, but hopefully I’ll be able to experiment with this in my lab sometime this autumn in order to get some more experience with it.

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