DCB PFC Demo with SMB Direct over RoCE (RDMA)


In this blog post we’ll demo Priority Flow control. We’re using the demo comfit as described in SMB Direct over RoCE Demo – Hosts & Switches Configuration Example

There is also a quick video to illustrate all this on Vimeo. It’s not training course grade I know, but my time to put into these is limited.

I’m using Mellanox ConnectX-3 ethernet cards, in 2 node DELL PowerEdge R720 Hyper- cluster lab. We’ve configured the two ports for SMB Direct & set live migration to leverage them both over SMB Direct. For that purpose we tagged SMB Direct traffic with priority 4 and all other traffic with priority 1. We only made priority lossless as that’s required for RoCE and the other traffic will deal with not being lossless by virtue of being TCP/IP.

Priority Flow Control is about making traffic lossless. Well some traffic. While we’d love to live by Queens lyrics “I want it all, I want it all and I want it now” we are limited. If not so by our budgets, than most certainly by the laws of physics. To make sure we all understand what PFC does here’s a quick reminder: It tells the sending party to stop sending packets, i.e. pause a moment (in our case SMB Direct traffic) to make sure we can handle the traffic without dropping packets. As RoCE is for all practical purposes Infiniband over Ethernet and is not TCP/IP, so you don’t have the benefits of your protocol dealing with dropped packets, retransmission … meaning the fabric has to be lossless*. So no it DOES NOT tell non priority traffic to slow down or stop. If you need to tell other traffic to take a hike, you’re in ETS country 🙂

* If any switch vendor tells you to not bother with DCB and just build (read buy their switches = $$$$$) a lossless fabric (does that exist?) and rely on the brute force quality of their products to have a lossless experience … could be an interesting experiment Smile.

Note: To even be able to start SMB Direct SMB Multichannel must be enabled as this is the mechanism used to identify RDMA capabilities after which a RDMA connection is attempted. If this fails you’ll fall back to SMB Multichannel. So you will have ,network connectivity.

You want RDMA to work and be lossless. To visualize this we can turn to the switch where we leverage the counter statistics to see PFC frames being send or transmitted. A lab example from a DELL PowerConnect 8100/N4000 series below.

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To verify that RDMA is working as it should we should also leverage the Mellanox Adapter Diagnostic and native Windows RDMA Activity counters. First of all make sure RDMA is working properly. Basically you want the error counters to be zero and stay that way.

Mellanox wise these must remain at zero (or not climb after you got it right):

  • Responder CQE Errors
  • Responder Duplicate Request Received
  • Responder Out-Of-Order Sequence Received
  • … there’s lots of them …

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Windows RDMA Activity wise these should be zero (or not climb after you got it right):

  • RDMA completion Queue Errors
  • RDMA connection Errors
  • RDMA Failed connection attempts

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The event logs are also your friend as issues will log entries to look out for like

PowerShell is your friend (adapt severity levels according to your need!)

Get-WinEvent -ListLog “*SMB*” | Get-WinEvent | ? { $_.Level -lt 4 -and $_. Message -like “*RDMA*” } | FL LogName, Id, TimeCreated, Level, Message

Entries like this are clear enough, it ain’t working!

The network connection failed.
Error: The I/O request was canceled.
Connection type: Rdma
Guidance:
This indicates a problem with the underlying network or transport, such as with TCP/IP, and not with SMB. A firewall that blocks port 445 or 5445 can also cause this issue.
 
RDMA interfaces are available but the client failed to connect to the server over RDMA transport.
Guidance:
Both client and server have RDMA (SMB Direct) adaptors but there was a problem with the connection and the client had to fall back to using TCP/IP SMB (non-RDMA).

 

To view PFC action in Windows we rely on the Mellanox Adapter QoS Counters

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Below you’ll see the number of  pause frames being sent & received on each port. Click on the image to enlarge.

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An important note trying to make sense of it all: … pauze and receive frames are sent and received hop to hop. So if you see a pause frame being sent on a server NIC port you should see them being received on the switch port and not on it’s windows target you are live migrating from. The 4 pause frames sent in the screenshot above are received by the switchport as you can see from the PFC Stats for that port.

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People, if you don’t see errors in the error counters and event viewer that’s good. If you see the PFC Pause frame counters move up a bit that’s (unless excessive) also good and normal, that PFC doing it’s job making sure the traffic is lossless. If they are zero and stay zero for ever you did not buy a lossless fabric that doesn’t need DCB, it’s more likely you DCB/PFC is not working Winking smile and you do not have a lossless fabric at all. The counters are cumulative over time so they don’t reset to zero bar resetting the NIC or a reboot.

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When testing feel free to generate lots of traffic all over the place on the involved ports & switches this helps with seeing all this in action and verifying RDMA/PFC works as it should. I like to use ntttcp.exe to generate traffic, the most recent version will let you really put a load on 10GBps and higher NICs. Hammer that network as hard as you can Winking smile.

Again a simple video to illustrate this on Vimeo.

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SMB Direct With RoCE in a Mixed Switches Environment


I’ve been setting up a number of Hyper-V clusters with  Mellanox ConnectX3 Pro dual port 10Gbps Ethernet cards. These Mellanox cards provide a nice amount of queues (128) for DVMQ and also give us RDMA/SMB Direct capabilities for CSV & live migration traffic.

Mixed Switches Environments

Now RoCE and DCB is a learning curve for all of us and not for the faint of heart. DCB configuration is non trivial, certainly not across multiple hops and different switches. Some say it’s to be avoided or can’t be done.

You can only get away with a single pair of (uniform) switches in smaller deployments. On top of that I’m seeing more and more different types of switches being used to optimize value, so it’s not just a lab exercise to do this. Combine this with the fact that DCB is an unavoidable technology in networking, unless it get’s replaced with something better and easier, and you might as well try and learn. So I did.

Well right now I’m successfully seeing RoCE traffic going across cluster nodes spread over different racks in different rows at excellent speeds. The core switches are DELL Force10 S4810 and the rack switches are PowerConnect 8132Fs. By borrowing an approach from spine/leave designs this setup delivers bandwidth where they need it a a price point they can afford. They don’t need more expensive switches for the rack or the core as these do support DCB and give the port count needed at the best price point.  This isn’t supposed to be the top in non blocking network design. Nope but what’s available & affordable today in you hands is better than perfection tomorrow. On top of that this is a functional learning experience for all involved.

We see some pause frames being sent once in a while and this doesn’t impact speed that very much. It does guarantee lossless traffic which is what we need for RoCE. When we live migrate 300GB worth of memory across the nodes in the different racks we get great results. It varies a bit depending on the load the switches & switch ports are under but that’s to be expected.

Now tests have shown us that we can live migrate just as fast with non RDMA 10Gbps as we can with RDMA leveraging “only” Multichannel. So why even bother? The name of the game low latency and preserving CPU cycles for SQL Server or storage traffic over SMB3. Why? We can just buy more CPUs/Cores. Great, easy & fast right? But then with SQL licensing comes into play and it becomes very expensive. Also storage scenarios under heavy load are not where you want to drop packets.

Will this matter in your environment? Great question! It depends on your environment. Sometimes RDMA is needed/warranted, sometimes it isn’t. But the Mellanox cards are price competitive and why not test and learn right? That’s time well spent and prepares you for the future.

But what if it goes wrong … ah well if the nodes fail to connect over RDAM you still have Multichannel and if the DCB stuff turns out not to be what you need or can handle, turn it of and you’ll be good.

RoCE stuff to test: Routing

Some claim it can’t be done reliably. But hey they said that for non uniform switch environments too Winking smile. So will it all fall apart and will we need to standardize on iWarp in the future?  Maybe, but isn’t DCB the technology used for lossless, high performance environments (FCoE but also iSCSI) so why would not iWarp not need it. Sure it works without it quite well. So does iSCSI right, up to a point? I see these comments a lot more form virtualization admins that have a hard time doing DCB (I’m one so I do sympathize) than I see it from hard core network engineers. As I have RoCE cards and they have become routable now with the latest firmware and drivers I’d love to try and see if I can make RoCE v2 or Routable RoCE work over different types of switches but unless some one is going to sponsor the hardware I can’t even start doing that. Anyway, lossless is the name of the game whether it’s iWarp or RoCE. Who know what we’ll be doing in 5 years? 100Gbps iWarp & iSCSI both covered by DCB vNext while FC, FCoE, Infiniband & RoCE have fallen into oblivion? We’ll see.

VEEAM Invests in Faster & More Efficient Data Protection With Backup & Replication 8


Ever more data to protect without breaking the systems or the bank

One of my major concerns today in IT, weather it is on premises or in the cloud, is the cost, time, reliability and feasibility of backup and restores. This true for most of us. Due to the environments in which I deliver my services my main issue with backups is the quantity of data. The amount of data is staggering and growth is not showing a downward trend.

The big four: CPU, Memory, Network & Storage

Over the years we have seen a vast increase in compute, memory, network and storage capabilities and pricing. CPUs are up to 18 cores per socket as I write this. DDR4 memory is here and the cost is relatively low. We have affordable 10Gbps networking to throw at the problem as well or in some case 8 to 16Gbps Fibre Channel. So when it comes to CPU, memory and network we’re pretty well served.

Storage is evolving as well and we’re getting ever bigger and, if you have the budget that is, faster storage arrays in different flavors. But it remains a challenge. First of all to get the right amount of IOPS and storage capacity at an affordable price point is a balancing act. Secondly when dealing with backups we need to manage the source IOPS & latency against the target. But that’s not all, while you might want to squeeze every last IOPS & 1ms latency out of your backup target you can’t carelessly do that to your source storage. If you do, this might constitute a Denial Of Service attack against your applications and services. Even today storage QoS is either non existent, in it’s infancy or at best limited to particular workloads on storage solutions.

The force multiplier: Backup software capabilities & approaches

If you’ve made sure the above 4 resources are not your killer bottle neck the backup software, methods algorithms and the approach used will be either your biggest problem or you best friends. You need your backup software to be:

  • Capable
  • Scalable
  • Fast
  • Configurable
  • Scale Out

There are some challenging environments out there. To deal with this backup software should be able to leverage the wealth of capabilities compute, network, memory & storage are offering to protect large amounts of data reliable and fast. This should be done smart and in an operationally supportable manner. VEEAM has been working on this for a long time and they keep getting better at this with every release and it allows for scale out designs in regards to backups targets.

VEEAM Backup & Replication 8.0

There are many improvements in v8 but a couple stand out.

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Consistency groups (Hyper-V)

Backup jobs can execute more than one VM backup task simultaneously from the same volume snapshot with “Allow Processing of Multiple VMs with a single volume snapshot”.

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This means you can reduce the number of snapshots significantly where in the past you needed a volume snapshot per VM. VEEAM limits the the maximum amount of VMs you can backup per snapshot to 4 when using software VSS and to eight with hardware VSS. They do this because under heavy load VSS/CSV sometimes has issues. This number can be tweaked to fit your needs (no all environments are created equally) with 2 registry values under HKLM\SOFTWARE\Veeam\Veeam Backup and Replication key:

  • MaxVmCountOnHvSoftSnapshot (DWORD)
  • MaxVmCountOnHvHardSnapshot (DWORD) registry values

Reducing the number of snapshots to be taken is good as it saves resources, speeds up things & as VSS can be finicky, not needing more than absolutely necessary is a good thing.

Backup I/O Control.

Another improvement is backup I/O Control which delivers capability to dynamically adjust the number of backup tasks based on IOPS latency. Under Options you’ll find a new Tabbed sheet, I/O Control. It contains the parallel processing option that used to be under “Advanced” tab in Veeam B&R 7.

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The idea is to move to a more “policy driven” approach for handling the load backups can put on the storage. Until now we’d configure a number of X amounts of tasks to run against the source storage in order to keep IOPS/Latency in check. But this is very static and in a dynamic / elastic “cloud” world this isn’t very flexible nor is it feasible to keep tuned to the best number for the current workload.

I/O Control let’s you set limits on how much latency is acceptable for your data stores. Removing or adding VMs to the data store won’t invalidate your carefully set number of tasks allowed as it’s now the latency that’s used to dynamically tune that number for you.

I/O control has two settings:

 “Stop assigning new tasks to datastore at: X ms” :VEEAM looks at the latency (IOPS) before assigning a proxy (backup target) to a virtual disk or won’t launch the task until the load has dropped.  This prevents the depletion of IOPS by launching to many backups.

“Throttle I/O of existing tasks at: Y ms”: This will throttle the IO of already running  backup jobs when needed due to some application workloads in the VMs running on the source storage kicking in. The backups will be throttled so they’ll take longer but they won’t kill the performance of the applications while they are running.

These two setting allow for the dynamic and on the fly tweaking of the number of backups tasks running as well as their impact on the storage performance. Once you have determined what latency values are acceptable to you you’re done, VEEAM handles the tweaking for you. The default values seems to reflect industry best practices (sustained > 20 ms is considered problematic)

The below screenshot is for the backup job log and shows latency being monitoredclip_image002

With VEEMA B&R v8 Enterprise + You can even do this per data store, meaning you can optimize this per backup source. This recognizes that is no “one sizes fits all perfectly” and allows for differentiation. Yet it does so in a way that does not compromise on the simplicity of use that VEEAM offers. This sounds easy but from experience I know this isn’t. VEEAM manages to offer a great balance between simplicity and functionality for companies of all sizes.

Select “Configure”

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In the “Datastore Latency Settings” you can add one, more or all data store you are protecting with VEEAM. This allows for differentiation when you have CSV that are used for SQL Server VMs versus stateless web servers of or other workloads that are not storage I/O intensive.

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Select the datastore (in our case the CSV volumes in Hyper-V Cluster)

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By selecting the desired datastore and clicking “Edit”  you can individually adjust the settings for that datastore.

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Conclusion

It looks like we have some great additional capabilities in an already very good solution. I’ll be using these new capabilities in real life scenarios to see how these work out for us and optimize the backups of the virtualized environment under my care. Hardware VSS Providers, SANs, CSV’s normally need some tweaking and care to make them run well, so that’s what we’ll be doing.

Where Does Storage QoS Live In Windows Server 2012 R2 Hyper-V


Back to basics to explain where storage QoS lives and how it works

In Windows Server 2012 R2 Hyper-V (and earlier) we have Hyper-V components called Virtualization Service Provider (VSP) and Virtualization Service Clients (VSC). In combination with the VMBUS the VSP and VSC components are what make virtualization perform well on Hyper-V.The Stor VSP/VSC are were the maximum IOPS functionality lives, aka as QoS Limit.

In a hosted hypervisor like Virtual PC or in a bare metal hypervisor without any “enlightment” the operating system inside a virtual machine is blissfully unaware of the fact it virtualized. Basically it sends hardware access requests using native drivers, but the requests are received by the virtual layer that intercepts them on behalf of the host OS by emulating hardware devices. This comes at a cost, namely performance, latency and losing device specific functionality.

In Hyper-V Microsoft provides the Integration Services (IS) for virtual machines running on Hyper-V which, in combination with the VMBus, avoids this overhead. So you should ways use them where and when possible. Two of the components in the IS are VSP and VSC. They are responsible for the communication between the Host OS or Parent Partition (where the VSP lives) and the Guest OS or Child Partition (where the VSC lives).

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There are 4 VSP & VSC components: Network, Video, HID and Storage. As you probably guessed we’re interested in the storage VSP & VSC (storVSP.sys & storvsc.sys) for the discussion at hand. While the Stor VSP lives in the host OS and the Stor VSC in the guest OS of every VM running on the host they communicate over the VMBus we mentioned and is designed to make communications as fast as possible (it’s a communication protocol that runs in memory, i.e. it’s very fast).

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The Minimum IOPS, also known as the Reserve is set per virtual disk but the threshold alerts for it are generated by the VHDMP. This is the VHD/VHDX parser and dependency property provider and this know all about the VHD/VHDX format with in itself is again a file on storage (DAS, CSV, SMB 3.0 File Share). This also happens to be where the Storage IO Balancer lives with which it collaborates, more on that below. You now see why QoS is not available for pass-through disk or iSCSI/FC storage in a VM, it requires a VHDX and is implemented at the virtual disk layer.

The QoS Limit (Maximum IOPS) is set at the virtual disk level via the Stor VSC and the Qos Limiter lives in the Stor VSP.

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So what do we know:

QoS Limit (Maximum IOPS) and QoS reserve (Minimum IOPS) are implemented at the virtual disk layer. So per VHDX in a particular VM.  It’s not available yet for shared VHDX, whether on the same host or not.

Unlike QoS Limit (Maximum IOPS), which is a hard cap, QoS reserve (Minimum IOPS) is a best effort not a hard minimum. It’s used to warn us, not as an enforcement. This works at the host level, where it will detect whether the VHDX can get get the minimum IOPS configured or not and can generate alerts if this happens. This tied to the QoS IO Balancer which is improved in R2 but it will still only spreads IOPS across multiple VMs on the same host, making sure they all get a fair share.

The key point here is that this process doesn’t work across multiple hosts in a cluster, over multiple clusters and stand alone member servers that might all be attached to the same storage system. Meaning that on shared, multi purpose storage we might have an issue. What if some VMs in a dedicated 4 node Hyper-V cluster dedicated to SQL Server virtualization is eating away all the IOPS. QoS IO Balancer will give each SQL Server VM a fair share of the IOPS but only within its host in that cluster. But if a VM on another host is consuming all IOPS, that’s out of it’s scope  That’s where the max cap comes to the rescue (at the virtual disk level) if you need it. Nice but not perfect. You can see now why the storage QoS minimum is implemented at the VHDMP layer, as this which is where the IO Balancer also lives. The fairness that the IO Balancer gives you a better change that the minimal reserve might be met and if it doesn’t you’ll get notified (you need to listen an react, I hope that’s obvious).

Also don’t forget that if you still have other physical servers that run file services, SQL Server or some data crunching apps you will find that those are blissfully ignorant of your QoS IO Balancer at the Hyper-V host level and of your QoS at the Hyper-V virtual disk level.

There is no multiple host QoS, there is no cluster wide QoS and there is no storage wide QoS in Windows. Perhaps you have some QoS your SAN but most of the time this has no knowledge of Hyper-V, the cluster and the virtual machines.

So the above this gives you an idea where does Microsoft might focus it’s attention in regards to storage IOPS  management (there are many more storage capabilities on my wish list) in vNext.

Any other options available today?

Other options are storage that is smart and has knowledge about the workload. This is nice but that means that it will come at a cost. For the moment GridStore with it’s virtual controller seems to be one of the better ones out there. Now I have heard people say Microsoft doesn’t get it and they’re doing do a bad job, but I do not agree. I have spoken to many people in the community and at MSFT and they have stated, even publicly, on stage, that they will keep investing in storage feature to enhance it in the versions to come. Take a look here at TechEd 2013 Session  MDC-B345: Windows Server 2012 Hyper-V Storage Performance.

Why would I like Microsoft to keep improving storage

When talking to storage vendors serving our needs, I always have some feedback. A lot of the advanced storage features don’t always work well in real life, especially if you combine a few. Don’t believe me? Talk to some experienced Windows engineers about the sorry state of many hardware VSS providers. Or how federation across storage systems falls apart the moment you combine it with application consistent snapshots or put a real heavy load on it. Not to cool when you paid for all those licenses which are tuned into “lab only” toys. Yes sometimes as a Windows user you feel like a second class citizen in storage land. A lot of storage systems are still very much a silo. Attempts to do storage federation without a hit on performance, making it load balance across SAN building blocks whilst making all the advanced features that have knowledge of the OS and hypervisor work reliably are not moving as fast as the race for ever more IOPS.

Sure I love the notion of 2 million IOPS, especially if you can get them with random write/read IO at super low latencies Smile. But there are other, sometimes more urgent needs and those seem to fall between the cracks as the storage vendors compete with each other and forget about the needs of their customers. If some storage vendors would shut up long enough to listen to customers they might be less surprised as to why those customers are interested in Storage Spaces.

So it would be kind of nice if Microsoft can work on this an include more evolved storage QoS capabilities in the box. I also like that approach for other reasons. Basically we will do everything we can with what Windows offers us inbox. It’s cost effective as long as you keep the KISS principle in mind and design it consciously. I assure you that often too much money is spent on 3rd party software because people don’t leverage what they have in box and drop the 20/80 rule. We do and you get the best TCO/ROI for our licenses possible. We don’t spend extra money on licenses, integration and support of third party products so we can spend it where it matters the most. It also makes upgrades easier as the complexity and the number of dependencies are lower on pure in box solution.On top of that we minimalize the distinct possibility that one or more 3rd party products will hold us hostage in an older infrastructure because they don’t support new versions of Windows fast, good and complete enough for us to upgrade.

How To Monitor Storage QoS Minimum IOPS & Identify VM & The Virtual Hard Disk In Windows Server 2012 R2 Hyper-V


At TechEd 2013 John Matthew & Liang Yang presented following session  MDC-B345: Windows Server 2012 Hyper-V Storage Performance. That was a great one. During this they demonstrated the use of WMI to monitor storage alerts related to Storage QoS in Windows Server 2012 R2. We’re going to go further, dive in a bit deeper and show you how to identify the virtual hard disk and the virtual machine.

One important thing in all this is that we need to have the reserve or minimum IOPS not being met, so we run IOMeter to make sure that’s the case. That way the events we need will be generated. It’s a bit of a tedious exercise.

So we start with a wmi notification query, this demonstrates that notifications are sent when the minimum IOPS cannot be met. The query is simply:

select * from Msvm_StorageAlert

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instance of Msvm_StorageAlert
{
    AlertingManagedElement = "\\\\TESTHOST01\\root\\virtualization\\v2:Msvm_ResourcePool.InstanceID=\"Microsoft:70BB60D2-A9D3-46AA-B654-3DE53004B4F8\"";
    AlertType = 3;
    Description = "Hyper-V Storage Alert";
    EventTime = "20140109114302.000000-000";
    IndicationTime = "20140109114302.000000-000";
    Message = "The ‘Primordial’ Hard Disk Image pool has degraded Quality of Service. One or more Virtual Hard Disks allocated from the pool is not reporting sufficient throughput as specified by the IOPSReservation property in its Resource Allocation Setting Data.";
    MessageArguments = {"Primordial"};
    MessageID = "32930";
    OwningEntity = "Microsoft-Windows-Hyper-V-VMMS";
    PerceivedSeverity = 3;
    ProbableCause = 50;
    ProbableCauseDescription = "One or more VHDs allocated from the pool (identified by value of AlertingManagedElement property) is experiencing insufficient throughput and is not able to meet its configured IOPSReservation.";
    SystemCreationClassName = "Msvm_ComputerSystem";
    SystemName = "TESTHOST01";
    TIME_CREATED = "130337413826727692";
};

That’s great, but what virtual hard disk of what VM is causing this? That’s the question we’ll dive into in this blog. Let’s go. On MSDN docs on Msvm_StorageAlert class we read:

Remarks

The Hyper-V WMI provider won’t raise events for individual virtual disks to avoid flooding clients with events in case of large scale malfunctions of the underlying storage systems.

When a client receives an Msvm_StorageAlert event, if the value of the ProbableCause property is 50 (“Storage Capacity Problem“), the client can discover which virtual disks are operating outside their QoS policy by using one of these procedures:

Query all the Msvm_LogicalDisk instances that were allocated from the resource pool for which the event was generated. These Msvm_LogicalDisk instances are associated to the resource pool via the Msvm_ElementAllocatedFromPool association.
Filter the result list by selecting instances whose OperationalStatus contains “Insufficient Throughput”.

So I query  (NOT a notification query!) the Msvm_ElementAllocatedFromPool class, click through on a result and select Show MOF.

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Let’s look at that MOF …In yellow is the GUID of our VM ID. Hey cool!

instance of Msvm_ElementAllocatedFromPool
{
    Antecedent = "\\\\TESTHOST01\\root\\virtualization\\v2:Msvm_ProcessorPool.InstanceID=\"Microsoft:B637F347-6A0E-4DEC-AF52-BD70CB80A21D\"";
    Dependent = "\\\\TESTHOST01\\root\\virtualization\\v2:Msvm_Processor.CreationClassName=\"Msvm_Processor\",DeviceID=\"Microsoft:b637f346-6a0e-4dec-af52-bd70cb80a21d\\\\6\",SystemCreationClassName=\"Msvm_ComputerSystem\",SystemName=\"
96CD7F7E-0C0A-42FE-96CB-B5550D937F27\"";
};

Now we want to find the virtual hard disk in question! So let’s do what the docs says and query Msvn_LogicalDisk based on the VM GUID we find the relates results …

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Look we got OperationalStatus 32788 which means InsufficientThroughput, cool we’re on the right track … now we need to find what virtual disk of our VM  that is. Well in the above MOF we find the device ID:     DeviceID = "Microsoft:5F6D764F-1BD4-4C5D-B473-32A974FB1CA2\\\\L"

Well if we then do a query for Msvm_StorageAllocationSettingData we find two entrties for our VM GUID (it has two disks) and by looking at the value InstanceID that contains the above DeviceID we find the virtual hard disk info we needed to identify the one not getting the minimum IOPS.

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HostResource = {"C:\\ClusterStorage\\Volume5\\DidierTest01\\Virtual Hard Disks\\DidierTest01Disk02.vhdx"};
HostResourceBlockSize = NULL;
InstanceID = "Microsoft:96CD7F7E-0C0A-42FE-96CB-B5550D937F27\\5F6D764F-1BD4-4C5D-B473-32A974FB1CA2\\\\L";

Are you tired yet? Do you realize you need to do this while the disk IOPS is not being met to see the events. This is no way to it in production. Not on a dozen servers, let alone on a couple of hundred to thousands or more hosts is it? All the above did was give us some insight on where and how. But using wbemtest.exe to diver deeper into wmi notifications/events isn’t really handy in real life. Tools will need to be developed to deal with this larger deployments. The can be provided by your storage vendor, your VAR, integrator or by yourself if you’re a large enough shop to make private cloud viable or if you are the cloud provider Smile.

To give you an idea on how this can be done there is some demo code on MSDN over here and I have that compiled for demo purposes.

We have 4 VMs running on the host.  One of them is being hammered by IOMeter while it’s minimum IOPS have been set to an number it cannot possibly get. We launch StorageQos to monitor our Hyper-V host.

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Just let it run and when the notification event that the minimum IOPS cannot be delivered on the storage this monitor will query WMI further to tell us what virtual disk or disks are  involved.  Cool huh! A good naming convention can help identify the VM and this tools works remotely against node so you can launch one for each node of the cluster. Time to fire up Visual Studio 2013 me thinks or go and chat to a good dev you might know to take this somewhere, some prefer this sort of work to the modern day version of CRUD apps any day. If you buy monitoring tools you might want them to have this capability.

While this is just demo code, it gives you an idea of how tools and solutions can be developed & build to monitor the Minimum IOPS part of Storage QoS in Windows Server 2012 R2. Hope you found this useful!