I Can’t Afford 10GBps For Hyper-V And Other Lies

You’re wrong

There, I said it. Sure you can. Don’t think you need to be a big data center to make this happen. You just need to think and work outside the box a bit and when you’re not a large enterprise, that’s a bit more easy to do. Don’t do it like a big name brand, traditionalist partner would do it (strip & refit the entire structural cabling in the server room, high end gear with big margins everywhere). You’re going for maximum results & value, not sales margins and bonuses.

I would even say you can’t afford to stay on 1Gbps much longer or you’ll be dealing with the fall out of being stuck in the past. Really some of us are already look at > 10Gbps connections to the servers, actually. You need to move from 1Gbps or you’ll be micro managing a way around issues sucking all the fun out of your work with ever diminishing results and rising costs for both you and the business.

Give your Windows Server 2012R2 Hyper-V environment the bandwidth it needs to shine and make the company some money. If all you want to do is to spent as little money as possible I’m not quite sure what your goal is? Either you need it or you don’t.  I’m convinced we need it. So we must get it. Do what it takes. Let me show you one way to get what you need.

Sounds great what do I do?

Take heart, be brave and of good courage! Combine it with skills, knowledge & experience to deliver a 10Gbps infrastructure as part of ongoing maintenance & projects. I just have to emphasize that some skills are indeed needed, pure guts alone won’t do it.

First of all you need to realize that you do not need to rip and replace your existing network infrastructure. That’s very hard to get approval for, takes too much time and rapidly becomes very expensive in both dollars and efforts. Also, to be honest, quiet often you don’t have that kind of pull. I for one certainly do not. And if I’d try to do that way it takes way too many meetings, diplomacy, politics, ITIL, ITML & Change Approval Board actions to make it happen. This adds to the cost even more, both in time and money. So leave what you have in place, for this exercise we assume it’s working fine but you can’t afford to have wait for many hours while all host drains in 6 node cluster and you need to drain all of them to add memory. So we have a need (OK you’ll need a better business case than this but don’t make to big a deal of it or you’ll draw unwanted attention) and we’ve taking away the fear factor of fork lift replacing the existing network which is a big risk & cost.

So how do I go about it?

Start out as part of regular upgrades, replacement or new deployments. The money is their for those projects. Make sure to add some networking budget and leverage other projects need to support the networking needs.

Get a starter budget for a POC of some sort, it will get your started to acquire some more essential missing  bits.

By reasonably cheap switches of reasonable port count that do all you need. If they’re readily available in a frame work contract, great. You can get it as part of the normal procedures. But if you want to nock another 6% to 8% of the cost order them directly from the vendor. Cut out the middle man.

Buy some gear as part of your normal refresh cycle. Adapt that cycle life time a bit to suit your needs where possible. Funding for operation maintenance & replacement should already be in place right?

Negotiate hard with your vendor. Listen, just like in the storage world, the network world has arrived at a point where they’re not going to be making tons of money just because they are essential. They have lots of competition and it’s only increasing. There are deals to be made and if you chose the right hardware it’s gear that won’t lock you into proprietary cabling, SPF+ modules and such. Or not to much anyway Smile.

Design options and choices

Small but effective

If you’re really on minimal budget just introduce redundant (independent) stand alone 10Gbps switches for the East-West traffic that only runs between the nodes in the data center. CSV, Live Migration, backup. You don’t even need to hook it up to the network for data traffic, you only need to be able to remotely manage it and that’s what they invented Out Off Band (OOB) ports for. See also an old post of mine Introducing 10Gbps With A Dedicated CSV & Live Migration Network (Part 2/4). In the smallest cheapest scenario I use just 2 independent switches. In the other scenario build a 2 node spine and the leaf. In my examples I use DELL network gear. But use whatever works best for your needs and your environment. Just don’t go the “nobody ever got fired for buying XXX” route, that’s fear, not courage! Use cheaper NetGear switches if that fits your needs. Your call, see my  recent blog post on this 10Gbps Cheap & Without Risk In Even The Smallest Environments.

Medium sized excellence

First of all a disclaimer: medium sized isn’t a standardized way of measuring businesses and their IT needs. There will be large differences depending on you neck of the woods Smile.

Build your 10Gbps infrastructure the way you want it and aim it to grow to where it might evolve. Keep it simple and shallow. Go wide where you need to. Use the Spine/Leaf design as a basis, even if what you’re building is smaller than what it’s normally used for. Borrow the concept. All 10Gbps traffic, will be moving within that Spine/Leaf setup. Only client server traffic will be going out side of it and it’s a small part of all traffic. This is how you get VM mobility, great network speeds in the server room avoiding the existing core to become a bandwidth bottleneck.

You might even consider doing Infiniband where the cost/Gbps is very attractive and it will serve you well for a long time. But it can be a hard sell as it’s “another technology”.

Don’t panic, you don’t need to buy a bunch of Nexus 7000’s  or Force10 Z9000 to do this in your moderately sized server room. In medium sized environment I try to follow the “Spine/Leaf” concept even if it’s not true ECMP/CLOSS, it’s the principle. For the spine choose the switches that fit your size, environment & growth. I’ve used the Force10 S4810 with great success and you can negotiate hard on the price. The reasons I went for the higher priced Force10 S4810 are:

  • It’s the spine so I need best performance in that layer so that’s where I spend my money.
  • I wanted VLT, stacking is a big no no here. With VLT I can do firmware upgrades without down time.
  • It scales out reasonably by leveraging eVLT if ever needed.

For the ToR switches I normally go with PowerConnect 81XX F series or the N40XXF series, which is the current model. These provide great value for money and I can negotiate hard on price here while still getting 10Gbps with the features I need. I don’t need VLT as we do switch independent NIC teaming with Windows. That gives me the best scalability wit DVMQ & vRSS and allows for firmware upgrades without any network down time in the rack. I do sacrifice true redundant LACP within the rack but for the few times I might really need to have that I could go cross racks & still maintain a rack a failure domain as the ToRs are redundant. I avoid stacking, it’s a single point of failure during firmware upgrades and I don’t like that. Sure I can could leverage the rack a domain of failure to work around that but that’s not very practical for ordinary routine maintenance. The N40XXF also give me the DCB capabilities I need for SMB Direct.

Hook it up to the normal core switch of the existing network, for just the client/server.(North/South) traffic. I make sure that any VLANs used for CSV, live migration, can’t even reach that part of the network.  Even data traffic (between virtual machines, physical servers) goes East-West within your Spine/Leave and never goes out anyway unless you did something really weird and bad.

As said, you can scale out VLT using eVLT that creates a port channel between 2 VLT domains. That’s nice. So in a medium sized business you’re pretty save in growth. If you grow beyond this, we’ll be talking about a way larger deployment anyway and true ECMP/CLOS and that’s not the scale I’m dealing with where. For most medium sized business or small ones with bigger needs this will do the job. ECMP/CLOS Spine/leaf actually requires layer 3 in the design and as you might have noticed I kind if avoid that. Again, to get to a good solution today instead of a real good solution next year which won’t happen because real good is risky and expensive. Words they don’t like to hear above your pay grade.

The picture below is just for illustration of the concept. Basically I normally have only one VLT domain and have two 10Gbps switches per rack. This gives me racks as failure domains and it allows me to forgo a lot of extra structural cabling work to neatly provide connectivity form the switches  to the server racks .image

You have a  scalable, capable & affordable 10Gbps or better infrastructure that will run any workload in style.. After testing you simply start new deployments in the Spine/Leaf and slowly mover over existing workloads. If you do all this as part of upgrades it won’t cause any downtime due to the network being renewed. Just by upgrading or replacing current workloads.

The layer 3 core in the picture above is the uplink to your existing network and you don’t touch that. Just let if run until there nothing left in there and you can clean it up or take it out. Easy transition. The core can be left in place or replaces when needed due to age or capabilities.

To keep things extra affordable

While today the issues with (structural) 10Gbps copper CAT6A and NICs/Switches seem solved, when I started doing 10Gbps fibre cabling of Copper Twinax Direct Attach was the only way to go. 10GBaseT wasn’t an option yet and I still love the flexibility of fibre, it consumes less space and weighs less then CAT6A. Fibre also fits easily in existing cable infrastructure. Less hassle. But CAT6A will work fine today, no worries.

If you decide to do fibre, buy OM3, you can get decent, affordable cabling on line. Order it as consumable supplies.

Spend some time on the internet and find the SFP+ that works with your switches to save a significant amount of money. Yup some vendor switches work with compatible non OEM branded SPF+ modules. Order them as consumable supplies, but buy some first to TEST! Save money but do it smart, don’t be silly.

For patch cabling 10Gbps Copper Twinax Direct Attach works great for short ranges and isn’t expensive, but the length is limited and they get thicker & more sturdy and thus unwieldy by length. It does have it’s place and I use them where appropriate.

Isn’t this dangerous?

Nope. Technology wise is perfectly sound and nothing new. Project wise it delivers results, fast, effective and without breaking the bank. Functionally you now have all the bandwidth you need to stop worrying and micromanaging stuff to work around those pesky bandwidth issues and focus on better ways of doing things. You’ve given yourself options & possibilities. Yay!

Perhaps the approach to achieve this isn’t very conventional. I disagree. Look, anyone who’s been running projects & delivering results knows the world isn’t that black and white. We’ve been doing 10Gbps for 4 years now this way and with (repeated) great success while others have to wait for the 1Gbps structural cabling to be replaced some day in the future … probably by 10Gbps copper in a 100Gbps world by the time it happens. You have to get the job done. Do you want results, improvements, progress and success or just avoid risk and cover your ass? Well then, choose & just make it happen. Remember the business demands everything at the speed of light, delivered yesterday at no cost with 99.999% uptime.  So this approach is what they want, albeit perhaps not what they say.

Preventing Live Migration Over SMB Starving CSV Traffic in Windows Server 2012 R2 with Set-SmbBandwidthLimit

One of the big changes in Windows Server 2012 R2 is that all types of Live Migration can now leverage SMB 3.0 if the right conditions are met. That means that Multichannel & SMB Direct (RDMA) come in to play more often and simultaneously. Shared Nothing Live Migration & certain forms of Storage Live Migration are often a lot more planned due to their nature. So one can mitigate the risk by planning.  Good old standard Live Migration of virtual machines however is often less planned. It can be done via Cluster Aware Updating, to evacuate a host for hardware maintenance, via Dynamic optimization. This means it’s often automated as well. As we have demonstrated many times Live Migration can (easily) fill 20Gbps of bandwidth. If you are sharing 2*10Gbps NICs for multiple purposes like CSV, LM, etc. Quality of Service (QoS) comes in to play. There are many ways to achieve this but in our example here I’ll be using DCB  for SMB Direct with RoCE.

New-NetQosPolicy “CSV” –NetDirectPortMatchCondition 445 -PriorityValue8021Action 4
Enable-NetQosFlowControl –Priority 4
New-NetQoSTrafficClass "CSV" -Priority 4 -Algorithm ETS -Bandwidth 40
Enable-NetAdapterQos –InterfaceAlias SLOT41-CSV1+LM2
Enable-NetAdapterQos –InterfaceAlias SLOT42-LM1+CSV2
Set-NetQosDcbxSetting –willing $False

Now as you can see I leverage 2*10Gbps NIC, non teamed as I want RDMA. I have Failover/redundancy/bandwidth aggregation thanks to SMB 3.0. This works like a charm. But when leveraging Live Migration over SMB in Windows Server 2012 R2 we note that the LM traffic also goes over port 445 and as such is dealt with by the same QoS policy on the server & in the switches (DCB/PFC/ETS). So when both CSV & LM are going one how does one prevent LM form starving CSV traffic for example? Especially in Scale Out File Server Scenario’s this could be a real issue.

The Solution

To prevent LM traffic & CSV traffic from hogging all the SMB bandwidth ruining the SOFS party in R2 Microsoft introduced some new capabilities in Windows Server 2012 R2. In the SMBShare module you’ll find:

  • Set-SmbBandwidthLimit
  • Get-SmbBandwidthLimit
  • Remove-SmbBandwidthLimit


To use this you’ll need to install the Feature called SMB Bandwidth Limit via Server Manager or using PowerShell:  Add-WindowsFeature FS-SMBBW

You can limit SMB bandwidth for Virtual machine (Storage IO to a SOFS), Live Migration & Default (all the rest).  In the below example we set it to 8Gbps maximum.

Set-SmbBandwidthLimit -Category LiveMigration -BytesPerSecond 1000MB

So there you go, we can prevent Live Migration from hogging all the bandwidth. Jose Baretto mentions this capability on his recent blog post on Windows Server 2012 R2 Storage: Step-by-step with Storage Spaces, SMB Scale-Out and Shared VHDX (Virtual). But what about Fibre Channel or iSCSI environments?  It might not be the total killer there as in SOFS scenario but still. As it turns out the Set-SmbBandwidthLimit also works in those scenarios. I was put on the wrong track by thinking it was only for SOFS scenarios but my fellow MVP Carsten Rachfahl kindly reminded me of my own mantra “Trust but verify” and as a result, I can confirm it even works to cap off Live Migration traffic over SMB that leverages RDMA (RoCE). So don’t let the PowerShell module name (SMBShare) fool you, it’s about all SMB traffic within the categories.

So without limit LM can use all bandwidth (2*10Gbps)


With Set-SmbBandwidthLimit -Category LiveMigration -BytesPerSecond 1250MB you can see we max out at 10Gbps (2*5Gbps).

Some Remarks

I’d love to see a minimum bandwidth implementation of this (that could include safety buffer for spikes in CSV traffic with SOFS). The hard cap limit might lead to some wasted bandwidth. In other scenarios you could still get into trouble. What if you have 2*10Gbps available but one of those dies on you and you capped Live Migration Traffic at 16Gbps. With one NIC gone you’re potentially in trouble until the NIC has been replaced. OK, this is not a daily occurrence & depending on you environment & setup this is less or more of a potential issue.

Adventures In RDMA – The RoCE Path Over DCB To Windows Server 2012 R2 SMB 3.0 Glory


On gloomy day, it was dark, grey and cold, we gave battle with RoCE & DCB (PFC/ETS). The fight was a long one, the battle field uncharted and we had only our veteran attitude towards adversity to guide us through the switch configurations. It seemed that no man had gone that far to the edges of the Windows Server 2012 empire. And when it came to RoCE & DCB meets Didier, I needed to show it that it had been conquered and was remembered of a quote in Gladiator:

Quintus: People RoCE/DCB configs should know when they are conquered.
Maximus: Would you, Quintus? Would I?


After many, many lonely & unsuccessful hours dealing with Performance monitor, switch configurations, reloads, firmware, drivers & Windows we got results:

… “it’s working” … “holey s* look at those numbers” …

On that dark day in a scarcely illuminated room, in the faint glare of the monitors even the CLI  of the switches in PUTTY felt like a grim cold place. But all that changed at as the impressive results brightened up the day and made all efforts seem worthwhile. “Didier Victor” I thought as I looked away from the screen, ‘”Once more”.image

But it has been a hard won victory. And should you fight this battle? We’ll let’s discuss this a bit now we’ve got your attention. RDMA is a learning process for many of us and neither Infiniband,  iWARP or RoCE are the one that need to win at this game. It’s you, via the knowledge you’ll gain working with RDMA technologies.

SMB Direct or SMB over RDMA comes in flavors

Infiniband (Mellanox)

That’s been here for a while. Has high cost associated (depends on where you come from) and also has a psychological barrier to it. Try discussing buying 10Gbps versus Infiniband with semi technical managerial types. You’ll know what I mean.

Deploying Windows Server 2012 with SMB Direct (SMB over RDMA) and the Mellanox ConnectX-2/ConnectX-3 using InfiniBand – Step by Step

iWARP (Chelsio / Intel)

RDMA but it’s TCP/IP offloaded to the card. It can leverage DCB but doesn’t require it.

Deploying Windows Server 2012 with SMB Direct (SMB over RDMA) and the Chelsio T4 cards using iWARP – Step by Step

RoCE (Mellanox)

“Infiniband over Ethernet” > so you “NEED” (no not a real hard requirement) DBC with PFC/ETS (DCBx can be handy) for it to work best. No need for Congestion Notification as it’s for TCP/IP but could be nice with iWARP (see above). Do note that you’ll need to configure your switches for DCB & that’s highly dependent on the vendor & even type of switches.

Deploying Windows Server 2012 with SMB Direct (SMB over RDMA) and the Mellanox ConnectX-3 using 10GbE/40GbE RoCE – Step by Step

Here’s an older overview of RDMA flavor’s pros & cons:image

Please see Jose Barreto’s excellent work on explaining SMB 3.0 over RDMA in his presentations at SNIA, TechEd and on his blog.

While I have heard of two people I have in my network working with Infiniband for SMB Direct and Windows Server 2012 (R2) most of us are doing 10Gbps. Pricing for Infiniband has a bad reputation. Not because Infiniband is super costly compared to 10/40Gbps (I’m told by most people who ask quotes are positively surprised) but when you can’t afford a Porsche you’re not shopping for a Ferrari either.  Especially not when a mid size sedan will serve al of your needs above and beyond the call of duty. On top of that you might have bought all that nice “converged network ready” 10Gbps gear some years ago. Some of us may be working towards 40Gbps but most are 10Gbps shops. My 40Gbps is “limited” to the inter links & uplinks. Meaning that we either go for iWarp or RoCE.


Which one is best of those two? Well, as the line is drawn between vendors. RoCE today equals Mellanox (yes the Infiniband vendor, RoCE is sometimes called “Infiniband on layer 4 over Ethernet layer 2”) and iWarp means Chelsio or Intel (their cards look a bit old in the teeth however).

You’ll find comparisons by both vendors claiming superiority for varied reasons. Here’s the Mellanox side http://www.mellanox.com/pdf/whitepapers/WP_RoCE_vs_iWARP.pdf & here’s Chelsio’s take http://www.chelsio.com/roce/ & http://www.moderntech.com.hk/sites/default/files/whitepaper/V09_iWAR_Summary_WP_0.pdf. It’s good to look at your needs and map them. But I cannot declare a winner. I did notice that at least one vendor of SOFS/CiB uses iWarp. Is that a statement? And if so about what? Price? Easy of use? Perfomance/Cost?

What I do find is that Chelsio is really hacking into RoCE as you can see here http://www.chelsio.com/wp-content/uploads/2011/05/RoCE-The-Grand-Experiment1.pdf, http://www.chelsio.com/roce-whitepaper/, http://www.chelsio.com/wp-content/uploads/2011/05/RoCE-FAQ-1204121.pdf So that begs the question are the right or are the scared of RoCE, as the Infiniband boys are out to eat their lunch?

My take on this for now

iWarp is way easier to get started. That’s for sure. RoCE  is firmware sensitive (NIC, Switches), driver sensitive (NIC). Configuring your switches (DCB) now is usually followed by a rebooting that switch (so you might not do that so easily in production and depending on where in the stack those switches live you really need to Force10 VLT or Cisco vPC, Arista MLAG  or a independent redundant switches to get away with it. RoCE loves green field. Stacking I hear you say? I don’t like stacking on that spot of the stack as firmware updates will get you to suffer through a single point of failure.

Disclaimer: RoCE in itself does not  DEMAND/REQUIRE DCB but the consensus is that it will work better, especially under heavy load. Weather SMB Direct over RoCE requires DCB is another question. For all practical purposes I’m working from the prerequisite it does for a production environment. But as you can do RoCE RDMA between to NIC with no DCB switch in between this indicates that the hard requirement for DCB is not there. Mind you not using DCB might not be smart in regards to QoS & error handling (no TCP/IP goodness handling this for you). But I’m no expert on this subject. Paul Grun however is and he’s involved with RoCE at  https://www.openfabrics.org/component/search/?searchword=Paul+grun&ordering=&searchphrase=all They tend to know their stuff. Read some of the comments below this article and you’ll know a lot http://www.hpcwire.com/hpcwire/2010-04-22/roce_an_ethernet-infiniband_love_story.html But PFC isn’t Walhalla either and some claim you can just forget about it and build non blocking networks. I guess you could if your pockets are deep enough Smile. And you might go a very long way without the need for RDMA. Many do … and when you talk to some network people & vendors they can’t agree either as everyone is on the same learning curve but from a different perspective. There is no one size fits all & it all depends.

iWarp doesn’t require DCB so you can get away with cheaper switches. Or, not so cheap switches that don’t support DCB (choose wisely). So cheaper switches is probably true on the low end. But, even very economically priced switches from DELL have good DCB support. Some other vendors who are more expensive don’t.

DCB is uncharted terrain for SMB Direct purposes & new to many for us. So if you want to do RDMA the easy way  … go iWARP. As said, the use of DCB for PFC/ETS is not mandatory in that case, you’ll get great results and it’s easy.  Mind you, you’ll still be dabbling with DCB if you want to do lossless magic in the switches Smile. Why you say? Well, that “converged network” story makes it kind of interesting to do so and PFC, DCBx/TLV is generic and can be leveraged for other things than iSCSI or FCoE.  And for all practical purposes SMB 3.0 with SMB Direct is a storage protocol since Windows Server 2012 made it so (CSV). Or do you do DCB for iSCSI/FCoE & iWarp for SMB Direct? After all there’s only 2 lossless queues to be had. But hey how many do you need? Choices, choices and no vast pool of experienced practitioners yet.

iWARP routes, it’s not bound by a single Ethernet broadcast domain. That could be useful info depending on your environment & needs. I’ll note that I leverage RDMA for East-West traffic, not north south & as such this could not be an issue. The time that I do “Shared Nothing Live Migration" from on premise to the cloud has not arrived yet.

The Mellanox cards in my neck of the woods were 35% cheaper than Chelsio (SFP+)

What about the scalability? “iWarp doesn’t scale that well” is stated left and right but I think that might often be based on older information. Chelsio makes a strong case for iWARP scalability. Especially when it comes to long distances, multiple hops & routing.

Again, your mileage may vary. But for “the smaller environments” who want to leverage RDMA with SMB 3.0 I’d say that iWarp is the easiest path to go & will do just fine. Now if you’re already into lossless Ethernet for iSCSI or working with FCoE you might have all the hardware you need & the experience to deal with DCB. The latter might not always be true however. Most people have Lossless Ethernet for iSCSI or FCoE set up by the vendor or consultants who’ll use well defined step by step guides. These do not exist for the RoCE variant of SMB 3.0 over RDMA.

The case for RoCE can be made as well.  Some claim that high volume of connections consumes memory when using iWARP and TCP’s flow and reliability controls are less suited for large-scale datacenters & cloud deployments due to performance issues. Where iWARP does not know multicast, RoCE does and that could be important to you.

So why did I or still do RoCE?

So why did I walk the walk? Basically because just talking the talk isn’t enough. We considered it an investment in our education. DCB is not going away (the abstraction isn’t their yet and won’t be for a while) and we need to gain knowledge of it to both handle it and make informed decisions. By the way once you go to lossless you might leverage DCB/PFC with iWarp as well just like you do for iSCSI to make it lossless (leveraging DCBx/TLV). Keep in mind that DCB is key in converged networking and as such deserves your attention. That’s why I chose not to avoid it but gave battle. DCB is all over the place when it comes to converged networking (iSCSI, FCoE), so we need to learn the good, the bad and the ugly. Until that day that perhaps, the hardware stack is that good, powerful & has so much bandwidth TCP/IP never needs it built in protection for packet loss. Hmmmmmm, I remember people saying that about 10Gbps, but then they wanted to send everything over 2*10Gbps pipes and it becomes an issue again?

It’s early days yet but you have to give credit to Microsoft for getting RDMA/DCB on the radar screen of the worlds virtualization & storage admins than ever before. It’s not a well established segment yet and it will be interesting to see how this all turns out. I do know that now that I’ve figured out a thing or two about RoCE, I won’t be intimidated & won’t make choices out of fear. And do remember that if you have plenty of idle CPU cycles & 10Gbps you might not even need RDMA. The value for me and my employers is the knowledge gained. DCB has it’s role to play but we’ll leverage iWARP or RoCE without a preference. Today you have 2 choices. RoCE is the newer one while iWarp has been around longer and both have avid proponents it seems.

I know one thing. If you need or want RDMA in any existing 10Gbps environment with minimal effort & no risk to existing switch infrastructure, you’ll use iWarp it seems.


You sit there staring at a truckload of VMs with 120GB of memory assigned in total being evacuated in +/- 70 seconds seconds, while doing a Shared Nothing Live Migration between the same hosts and without consuming CPU load …  and have DCB for SMB 3.0 running on your switches … Yes!


Remember, “What we do in life, echo’s in eternity” Winking smile You might think now that I’m a bit nutty, but I assure you that in my quest to find someone who had hands on experience configuring DCB on switches for SMB Direct with RoCE I had to turn to myself as no one seems to have done it.  I’ll be sharing more info on our setup and configurations in the future. Once you wrap your head around the concepts, you understand why things are done and how. There in lies the value for me.

Windows Server Backup Benefits from Improvements in Windows Server 2012


In certain environments we backup VMs and any remaining physical hosts using Windows Backup. Before you all think this is ridiculous, I advise you to think again. With some automation you can build a very reliable agentless backup solution with the built in functionality. Windows Server 2012 brings good news for the smaller & perhaps low budget environments. Windows Server Backup is now capable of doing host level backups of the Hyper-V guest stored on Clustered Shared Volumes. This was not the case in Windows 2008 R2 and it is a vast improvement.This change is due to the fact that CSV has been changed not to require specialized API capable of dealing with it’s intricacies. All backup products now can backup CSVs without specialized APIs.

This is, linked to huge improvements in how a CSV behaves during a backup. In the past, when you started a backup, the CSV ownership would be moved to the node that runs the backup and all access by other nodes was in redirected mode for the duration of the backup. Unless you used a hardware VSS provider, which were not trouble free either. If your backup software did not understand CSVs and use the CSV APIs you were out of luck. From Windows Server 2012 on you are only in redirected I/O mode for the time it takes to create the VSS snapshot. The rest of the backup duration your nodes access the CDV disk in direct mode. So back to Windows Server Backup. You cannot up the CSV as disk volume but you can select Hyper-V from the items to include in the backup.


That will show all VMs running on that host, meaning you cannot backup VMs running on another host. Compared to Windows Server 2008 R2 where using the native Windows backups  with VMs on a CSV LUN meant using in guest backups this a major improvement.

Some Approaches to Using Windows Server Backup

Sometime we run the backups to local disk and regularly copy those off to a file share. This has the benefit of providing the backup versioning you can from using a local disk. The draw back is that the backups can be rather big.

In VMs, that is with backups in the guest, we run those backups to a file share over a 1Gbps management network. Performance is good, but it leaves us with the issue that there is no versioning.

For that reason our backup script copies the entire backup folder for a server to an archive folder on that same JBOD. Depending on how much space you have and need you can can configure the retention time of these older backups. This way you can keep a large number of backups over time.  A script runs every day that deletes the older backups based on the chosen retention time so you don’t run out of space.

There is one way around the lack of versioning when writing backups to a share and that is to mount a VHD on a file share locally to the host where you are running a backup or use pass through disk inside the VM. While you can get away with this becomes rather messy due to management & flexibility drawbacks of pass through disks. Mounting a VHD on a file share inside a VM is also a performance issue. So while possible and viable in certain scenarios I don’t use this for more than a few hosts and those are physical ones.

We had hoped that Windows Server 2012 with its support for VSS snapshots on SMB 3.0 shares would have enabled backup versioning in Windows Backup, just like it can do for backups to local disk. Unfortunately this is not the case. You’ll still get the same warning when backing up from a Windows Server 2012 host to an SMB 3.0 share as you used to get with previous versions:


How fast are backups and restores?

The largest environment is a couple of Physical servers, a two node Hyper-V cluster and about 22 virtual machines. That includes some with a larger amount of data. The biggest being 400 GB. Full backups are run weekly at night on all servers over 1Gbps and this works just fine.

We can backup a VM of with a 50GB VHD (about 50% to 75% in use) and copy that backup to the archive folder in 20 minutes. We backup AND copy to archive a VM’s C: Drive (20GB of data) and a D: Drive (190GB of data), 2 separate VHD  in 2.5 hours.

For some statistics. A bare metal restore of a VM or physical host over 1Gbps with a single VHD or volume with the OS, applications and some data takes us 30 tot 35 minutes in real life due to the overhead of setting a new VM up. I you just want to restore individual data you can do that as well. You can even mount the backup VHD and recover them via the Windows Explorer.

This is what a the logging we do and e-mail to the sys admins looks like:


Where else do the Windows Server 2012 improvements help?

Data Deduplication

Now there is some good news. We ran ddpeval.exe against the JBOD LUNS where we store these archived backups and got some great results. We also copied such an archive folder to a Windows Server 2012 Host and ran data deduplication against it. In that test we achieved a 84%-85% deduplication rate depending on how many versions of the backups we archive and what the delta is during that time frame.  The latter is important. If we run dedupe only against domain controller backup archives we get up to 94%. Deduplication should not not impact restore performance to much because in 99% of the cases you revert to the last backup which sits in the WindowsBackup Folder. Only if you need older backups you will work against the deduped files, unless the archive folder is on the same LUN as the original backups. I’ don’t have real life info about restores yet. Just a small lab test.

SMB 3.0 & Multichannel

In Windows Server 2012 you also get all benefits of SMB 3.0 and MultiChannel for your backup traffic.

Not your grandfathers ChkDsk

The vastly improved ChkDsk is a comfort for worried minds when it comes to fixing potential corruption on a large LUN. Last but not least, the FLUSH command in NTFS makes using cheaper data disks safer.


The VHDX format allows for 64TB. That means your Windows Server backup can now handle more than 2TB LUNs. This should be adequate Smile


With some creativity and automation via scripting you can leverage the Windows Backup to be a nice and flexible solution. Although I feel that providing backup versioning to a file share is an improvement that is missing  the new features help out a lot and all in all, it’s not bad at all! So you see, even smaller organizations can benefits seriously from Windows Server 2012 and get more bang for their bucks.