Cluster Shared Volumes without Active Directory

Introduction

Cluster Shared Volumes without Active Directory will come online if certain conditions are met. Basically, when the cluster can form. That’s what we’ll talk about here. There are a lot of things to consider when virtualizing your Active Directory environment, partially or completely. Too much for this blog post alone and much of it has been discussed before. Here I’ll discuss when people count on their Cluster Shared Volumes coming online when active directory is not available but are disappointed and think that it’s a bug or a broken promise. It is not! We know that since Windows Server 2012 the CSVs coming online do not depend on Active Directory being available (thanks to the local CLIUSR account being used for cluster starts).

Cluster Shared Volumes without Active Directory

So, let’s address getting your Cluster Shared Volumes online when AD is not available. The things to realize is that not having Active Directory has been taken care off. The thing that still can go wrong is that the cluster doesn’t come on line properly and that means that the CSV LUNs won’t be online as those are cluster resource. Hyper-V can boot the VMs without the cluster being formed but as the VMs reside on a CSV and those are not available, that’s what’s causing the problem. That means that getting your cluster to come up is the real issue.

Getting your cluster to come up is the real issue.

If cluster shared volumes can come up without a domain controller / AD being available since Windows Server 2012 (Failover Clustering and Active Directory Integration) how is it that some many people still have issues with it? How do you make this work for you? You can use a disk witness to protect you in most cases. When you have a file share or cloud witness you can take some step to avoid running into this issue.

There is a great article on cluster behavior here: Failover Cluster Node Startup Order in Windows Server 2012 R2 (the same rules apply for Windows Server 2016). Read it and you’ll notice that the behavior differs depending on whether you have a witness defined and whether that witness is a witness disk or a file share or cloud witness. The disk witness has a copy of the cluster database and if available will help you out of any situation where the paxos on the disk witness (if it’s available) is more recent then the one on the cluster node as the node will download the cluster database info from the disk witness. But a file share or cloud witness don’t have a copy, so they have a small disadvantage under certain scenarios. CSV’s that won’t come up is when booting the nodes in the wrong order when using a file share or cloud witness is one of those scenarios but not having AD isn’t the root cause of this.

Some people will never notice this issue at all, especially not when they have disk witness, but when they do, it might be at a very inconvenient moment in time. Examples of where this situation can occur are a single cluster environment where the domain controllers are running on CSV and high available in that cluster that was shut down completely, the cluster has a file share witness and the nodes are started in the wrong order.

Making sure your CSVs come online = clustering being formed

Well for one make sure you are using Windows Server 2012 or higher for your cluster. That’s a given.

Beyond that you basically just need to know what to do in what scenario to get your cluster up and running so you won’t have issues with getting the CSV to come up. You just have to follow some rules of thumb and you’ll be fine. Also, there’s almost always a way to get out of pickle, just don’t panic. But also remember that you can make your live easier when you design your solutions with failure in mind and by knowing your options so you can act correctly. I my example I’ll be using Hyper-V cluster with CSVs but the same goes for SOFS, SQL Server clusters leveraging CSVs etc.

Planned down time

If you’re shutting down a complete cluster you have two options to make sure things go a smooth as possible.

Option 1 – A clean cluster shutdown by the book

  • Shut down the workload, i.e. the VMs.
  • Stop the cluster
  • Shutdown the Cluster nodes.
  • Boot the cluster nodes. You can start with any you like. The CSVs will come on line. You will be able to start the VMs. Do start with the domain controllers and wait for them to come on line before starting the others.

During this you’ll see some “collateral” events, errors, warnings due to Active Directory not being available. The cluster name has issues without Active Directory but that a management connection point, it doesn’t mean the cluster doesn’t work. Once Active Directory is available the cluster name will come on line automatically when the default failure policy restarts it. You can also manage the cluster via RDP or console by connection to “.” locally on that node or use the running node name. You can also try to bring cluster name on line manually when Active Directory is up and running.

Option 2 – A clean cluster shutdown as it happens most of the times in real life

Which is one a lot of people do to keep part of the work load running as long as possible.

  • Shut down the no critical workload, i.e. the VMs.
  • Pause a node so the critical workloads live migrate to other nodes
  • When the node is paused, shut down the node.
  • You rinse and repeat this until the last node is left with only the most critical VMs

clip_image002

  • Finally, you stop the workload on that last cluster node and shut it down as well.
  • Now comes the critical part: Remember what node you shut down last. You have to start that one first and you’ll see that your CSV will come on line. If you boot another node, you might panic as the CSV will not come on line.

Now I need to correct this a little bit. With a disk witness you are OK whatever node you boot. When the paxos numbers on the first node to boot and the disk witness are compared the most recent copy will be used. Either the local one on the node will be used directly or after it has been updated with the data form the disk witness. To make things simple for the ops team I always tell them to note the last node they shut down anyway no matter what type of witness they have. It’s good info to have.

With a file share or cloud witness the shutdown/startup order really comes into play. The reason this happens is that by shutting down node by node we end up with a one node cluster (last man standing).  When that’s shut down that’s the only node that knows about the last (potential) changes in the cluster as it holds a copy of the cluster database. Remember that a files hare or a cloud witness has no copy of the cluster database. That’s why the last node to be shut down has to come on line first when comparing the paxos numbers with the witness as that node can form a cluster. If the node that boots first does not hold the most recent paxos number it cannot download the cluster databases info from the file share or cloud witness. Such a node cannot form a cluster and bring the CSVs online. If the first node to boot was the last one to shut down, it can form a cluster and the CSVs will come on line. This is the big difference with option one where you shut down the entire cluster and then take the nodes of line.

You might not know or remember the order. If that’s the case you still have options like starting the cluster node with the -fixquorum option (net.exe start clussvc /forcequorum) at the risk of loosing some cluster changes that are not in the local cluster database.

No need to go to immediately backups, extract the domain controller VMs from SAN snapshots or mount a LUN to a different machine to extract the VM files for the DC or so. Don’t panic!

One or more failed nodes

Well as long as the cluster survives your domain controller VMs should fail over. Keep ‘m on separate node (anti-affinity), separate CSV LUNs, if possible separate clusters if all domain controller virtual machines are going to be running high available on a cluster node and that cluster is still functional after all. No issues here.

Total cluster failure

The cluster nodes all show due to a “global” BSOD or are turned off due to a power failure or a storage array crash. This is more the realm of bad dreams I know, it does happen. Often things will recover and you’ll be fine but you can do your part. The same rules apply, get the cluster to form and you’ll have your CSVs on line. In a bad case -fixquorum is your friend but normally it’s not your first option. In the worst case you’ll need recovery from backup of the cluster or rebuild it. It’s a very bad day if it comes to that. And cluster recovery is not the subject of this post.

Conclusion

Don’t blame Active Directory and start troubleshooting or fixing the wrong problem. So yes, CSV will come on line when certain conditions are met and you can work yourself out of a pickle if needed. But during a disaster that’s only extra work and stress you might not want to worry about if you can avoid it. It’s good to know how to resolve issues around CSVs not coming online when the shit hits the fan as even the best laid out plans tend to get side tracked by reality when disaster strikes.

If you cannot guarantee control over all the prerequisites and might not have the skills in please when needed, you might consider other options. Some of these are actually the best practices of the past when a CSV would indeed not come on line without active directory in any way. This is great for AD related issues but not for you offline CSVs, they need the cluster to form properly!

Sure, you can run the domain controller virtual machines on local storage, and not made high available. This cloud be on one of the cluster nodes (*) or on a stand-alone Hyper-V host. Having a physical domain controller is also a possibility. This helps avoid issues with AD in virtualized environments as many other services are very dependent on them and it’s good to have on one available all of the time and get them back on line a.s.a.p..

I’ll leave you with the fact that virtualizing domain controllers can be done but it pays to study up on how to do it well and test your assumptions in the lab. There is a lot of information on virtualizing domain controllers for a reason. Read it and process what you’ve learned from it. You might find that this CCV thingies is not the most complex subject to deal with.

(*) Please note that some cluster deployments like HCI based on S2D do not support running other (local) storage in addition to the boot OS and the S2D storage pool volumes.

New SMB Instances in Windows Server 2016

Introduction

I’m pretty sure you all know / remember that in Windows Server 2012 R2 one of the improvements we got for SMB 3 was the default and the CSV instance. You can take a peak here at my slide deck from a presentation I gave at the Microsoft Technical Summit in Berlin 2014 Failover Clustering- What’s new in Windows Server 2012 R2

image

You can also read more on TechNet here.

We have New SMB Instances in Windows Server 2016

I’m happy to see this concept being expanded in the new SMB workloads. When playing  with Windows Server 2016 TPv5 I you’ll notice that we now have gotten extra SMB instances:

image

So what are these New SMB Instances in Windows Server 2016 about?

Default: This is what we had before, it’s nonspecific default SMB traffic, such as file shares

CSV: Also already known since Windows Server 2012 R2. This is the CSV traffic. This got isolated for better resiliency and isolation of issues. The goal was not to let CSV SMB issues affect default SMB traffic.

SR: This stands for Storage Replica. The purpose of this instance is the same as for CSV, isolate and make SMB on the whole more resilient.

SBL: This stands for “Storage Bus Layer”, which is related to Storage Spaces Direct replication traffic. The Storage Bus Layer is now called the Software Storage Bus (SSB). Again, isolated in its own instance for better resilience and isolation of issues. You can find more on the Software Storage Bus in Storage Spaces Direct and its use of SMB here Storage Spaces Direct – Under the hood with the Software Storage Bus

Picture by Microsoft®

“SSB uses SMB3 and SMB Direct as the transport for communication between the servers in the cluster. SSB uses a separate named instance of SMB in each server, which separates it from other consumers of SMB, such as CSVFS, to provide additional resiliency. Using SMB3 enables SSB to take advantage of the innovation we have done in SMB3, including SMB Multichannel and SMB Direct. SMB Multichannel can aggregate bandwidth across multiple network interfaces for higher throughput and provide resiliency to a failed network interface. SMB Direct enables use of RDMA enabled network adapters, including iWARP and RoCE, which can dramatically lower the CPU overhead of doing IO over the network and reduce the latency to disk devices”

Funny anecdote: while doing some research I stumbled upon the MSDN article MSFT_SmbShare class. As you can see in the screenshot below the name was mistakenly put at “Storage Bus Later” but it should be Storage Bus Layer or as it’s now called the Software Storage Bus:

clip_image002

Now that will be fixed soon or by the time you read this blog post. All fun aside, if you want to see what that Software Storage Bus is capable off look at this blog post and video by Ned Pyle on what Claus Joergenson achieved already in 2015 with this technology. Amazing results!

Defragmenting your CSV Windows 2012 R2 Style with Raxco Perfect Disk 13 SP2

When it comes to defragmenting CSV it seemed we took a step back when it comes to support from 3rd party vendors. While Windows provides for a great toolset to defragment a CSV it seemed to have disappeared form 3r party vendor software. Even from the really good Raxco Perfect disk. They did have support for this with Windows 2008 R2 and I even mentioned that in a blog.

If you need information on how to defragment a CSV in Windows 2012 R2, look no further.There is an absolutely fantastic blog post on the subject How to Run ChkDsk and Defrag on Cluster Shared Volumes in Windows Server 2012 R2, by Subhasish Bhattacharya one of the program managers in the Clustering and High Availability product group. He’s a great guy to talk shop to by the way if you ever get the opportunity to do so. One bizarre thing is that this must be the only place where PowerShell (Repair-ClusterSharedVolume cmdlet) is depreciated in lieu of chkdsk.

3rd party wise the release of Raxco Perfect Disk 13 SP2 brought back support for defragmenting CSV.

image

I don’t know why it took them so long but the support is here now. It looks like they struggled to get the CSVFS (the way CSV are now done since Windows Server 2012) supported. Whilst add it, they threw in support for ReFS by the way. This is the first time I’ve ever seen this. Any way it’s here and that’s good because I have a hard time accepting that any product (whatever it does) supports Hyper-V if it can’t handle CSV, not if you want to be taken seriously anyway. No CSV support equals = do not buy list in my book.

Here’s a screenshot of Perfect disk defragmenting away. One of the CSV LUNs in my lab is a SSD and the other a HDD.

image

Notice that in Global Settings you can tweak the behavior when defragmenting optimization of various drive types, including CSVFS but you just have to leave the default on unless you like manual labor or love PowerShell that much you can’t forgo any opportunity to use it Winking smile

image

Perfect disk cannot detect what kind of disks you have behind the CSV LUN so you might want to change the optimization method if you’re running SSD instead of HHD.

image

I’d love for Raxco to comment on this or point to some guidance.

What would also be beneficial to a lot of customers is guidance on defragmentation on the different auto-tiering storage arrays. That would make for a fine discussion I think.

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.