Author Archives: workinghardinit

Between Windows Server 2016 TPv3 and TPv4 we moved from ReFS version 2.0 to 3.0

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Introduction

The fact that between Windows Server 2016 TPv3 and TPv4 we moved from ReFS version 2.0 to 3.0 is something I stumbled upon by accident. In  Windows Server 2016 we’re getting a new and improved version of ReFS. ReFS, (Resilient File System) was introduced in Windows Server 2012.

Since Windows Server 2016 Technical Previews we got a new capability with fsutil as it now knows about ReFS. Using fsutil we can check for the version of ReFS. The command you need for that is:

fsutil fsinfo refsinfo <driveletter>

This is something we definitely could not do in windows Server 2012 or Windows Server 2012 R2. I stumbled onto this by accident while experimenting with ReFS in the previews. Considering the ReFS focus in Windows Server 2016 R2 this is not a surprise. I noticed that.

TPv3 to TPv4 = ReFS version 2.0 to 3.0

In Windows 2016 TPv2 and TPv3 fsutil fsinfo refsinfo reports ReFS 2.0.

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After installing (clean install) TPv4 I was faced with the fact that my existing ReFS formatted volumes showsed up as RAW, they could not be mounted.

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I had to reformat those (or move them to a TPv3 installation to recuperate the data). When investigating this on Windows Server 2016 TPv4 with fsutil I noticed that we are at ReFS version 3.

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The same actually goes for a ReFS version 3.0 volume, it’s RAW in Windows Server 2016 TPv3, unusable.

The important thing to keep in mind going forward is that from my upgrade experiences I learned that ReFS version 2 is not usable in TPv4. Keep that in mind when upgrading. You might want to get your data copied to NTFS or so if you still need it.

I also don’t know if in future technical preview release or whatever they are called then we’ll see 3.1 or 4.0 arrive. But it’s something I’ll watch very carefully when moving to those versions Smile.

Hyper-V Amigos Podcast Episode 2 – WorkingHardInIT

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Just a quick post to let you know the second Hyper-V amigo podcast is on line. You can find it at Hyper-V Amigos Podcast Episode 2 – Didier Van Hoye

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In this episode Carsten Rachfahl (https://www.hyper-v-server.de) talks with his fellow Hyper-V Amigos buddy Didier Van Hoye – that would be me. Carsten and I are both Microsoft Cloud and Datacenter Management MVP. We’ll  talk about our passion for technology, when I started in computing, what it means to be an MVP and so many more things.

It was fun doing and I hope you have fun listening.

A first look at shared virtual disks in Windows Server 2016

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Introduction to shared virtual disks in Windows Server 2016

Time to take a first look at shared virtual disks in Windows Server 2016 and how they are set up. Shared VHDX was first introduced in Windows Server 2012 R2. It provides shared storage for use by virtual machines without having to “break through” the virtualization layer. This way is still available to us in Windows Server 2016. The benefit of this is that you will not be forced to upgrade your Windows Server 2012 R2 guest clusters when you move them to Windows Server 2016 Hyper-V cluster hosts.

The new way is based on a VHD Set. This is a vhds virtual hard disk file of 260 MB and a fixed or dynamically expanding avhdx which contains the actual data. This is the “backing storage file” in Microsoft speak. The vhds file is used to handle the coordination of actions on the shared disk between the guest cluster nodes?

Note that an avhdx is often associated with a differencing disk or checkpoints. But the “a” stands for “automatic”. This means the virtual disk file can be manipulated by the hypervisor and you shouldn’t really do anything with it. As a matter of fact, you can rename this off line avhdx file to vhdx, mount it and get to the data. Whether this virtual disk is fixed or dynamically expanding doesn’t matter.

You can create on in the GUI where it’s just a new option in the New Virtual Hard Disk Wizard.

Or via PowerShell in the way you’re used to with the only difference being that you specify vhds as the virtual disk extension.

In both cases both vhds and avhdx are created for you, you do not need to specify this.

You just add it to all nodes of the guest cluster by selecting a “Shared Drive” to add to a SCSI controller …

… browsing to the vhds , selecting it and applying the settings to the virtual machine. Do this for all guest cluster nodes

Naturally PowerShell is your friend, simple and efficient.

Rules & Restrictions

As before shared virtual disk files have to be attached to a vSCSI controller in the virtual machines that access it and it needs to be stored on a CSV. Both block level storage or a SMB 3 file share on a Scale Out File Server will do for this purpose. If you don’t store the shared VHDX or VHD Set on a CSV you’ll get an error.

Sure for lab purposes you can use an non high available SMB 3 share “simulating” a real SOFS share but that’s only good for your lab or laptop.

The virtual machines will see this shared VHDX as shared storage and as such it can be used as cluster storage. This is an awesome concept as it does away with iSCSI or virtual FC to the virtual machines in an attempt to get shared storage when SMB 3 via SOFS is not an option for some reason. Shared VHDX introduces operational ease as it avoids the complexities and drawbacks of not using virtual disks with iSCSI or vFC.

In Windows Server 2012 R2 we did miss some capabilities and features we have come to love and leverage with virtual hard disks in Hyper-V. The reason for this was the complexity involved in coordinating such storage actions across all the virtual machines accessing it. These virtual machines might be running on different hosts and, potentially the shared VHDX could reside on different CSVs. The big four limitations that proved to be show stopper for some use cases are in my personal order of importance:

  1. No host level backup
  2. No on line dynamic resize
  3. No storage live migration
  4. No checkpoints
  5. No Hyper-V Replica support

I’m happy to report most of these limitations have been taken care of in Windows Server 2016. We can do host level backups. We can online resize a shared VHDX and we have support for Hyper-V replica.

Currently in 2016 TPv4 storage live migration and checkpoints (both production and standard checkpoints) are still missing in action but who knows what Microsoft is working on or has planned. To the best of my knowledge they have a pretty good understanding of what’s needed, what should have priority and what needs to be planned in. We’ll see.

Other good news is that shared VHDX works with the new storage resiliency feature in Windows Server 2016. See Virtual Machine Storage Resiliency in Windows Server 2016 for more information. Due to the nature of clustering when a virtual machine loses access to a shared VHDX the workload (role) will move to another guest cluster node that still has access to the shared VHDX. Naturally if the cause of the storage outage is host cluster wide (the storage fabric or storage array is toast) this will not help, but other than that it provides for a good experience. The virtual machine guest cluster node that has lost storage doesn’t go into critical pause but keeps polling to see if it regains access to the shared VHDX. When it does it’s reattached and that VM becomes a happy fully functional node again.

It also supports the new Storage Qos Policies in Windows Server 2016, which is something I’ve found during testing.

Thanks for reading!

ReFS vNext Block Cloning and ODX

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Introduction

With Windows Server 2016 we also get a new version of ReFS, which I’ll designate aptly as ReFS vNext. It offers a few new abstractions that allow applications and virtualization to control how files are created, copied and moved. The features that are crucial to this are block cloning and data tiering.

Block cloning allows to clone any block of a file into any other block of another file. These operations are based on low cost metadata actions. Block cloning remaps logical clusters (physical locations on a volume) form the source region to the destination region. It’s important to note that this works within the same file or between files. This combined with “allocate on write” ensures isolation between those regions, which basically means files will not over write each other’s data if they happen to reference the same region and one of them writes to that region. Likewise, for a single file, if a region is written to, that changed data will not pop up in the other region. You can learn more about it on this MSDN page on block cloning which explains this further.

ReFS vNext does not do this for every workload by default. It’s done on behalf of an application that calls block cloning, such as Hyper-V for example when merging VHDX files. For these purposes the meta data operations counting references to regions make data copies within a volume fast as it avoids reading and writing of all the data when creating a new file from an existing one, which would mean a full data copy. It also allows reordering data in a new file as with checkpoint merging and it also allows for “data projection” where data can be projected form one area in to another without an actual copy. That’s how speed is achieved.

Now some of the benefits of ReFS vNext are tied into Storage Space Direct. Such as the tiering capability in relation to the use of erasure encoding / parity to get the best out of a fast tier and a slower tier without losing too much capacity due to multiple full data copies. See Storage Spaces Direct in Technical Preview 4 for more information on this.

I’m still very much a student of all this and I advise you to follow up via blogs and documentation form Microsoft as they become available.

What does it mean?

In the end it’s all about making the best use of available resources. The one that you already have and the one that you will own in the future. This lowers TCO and increases ROI. It’s not just about being fast but also optimizing the use of capacity while protecting data. There is one golden rule in storage: “Thou shalt not lose data”.

For now, even when you’re not yet in a position to evaluate Storage Space Direct, ReFS vNext on existing storage show a lot of promise as well. I have blogged about file creation speeds (VHDX files) in this blog post: Lightning Fast Fixed VHDX File Creation Speed With ReFS vNext on Windows Server 2016. In another blog post, Accelerated Checkpoint merging with ReFS vNext in Windows Server 2016 you can read about the early results I’ve seen with Hyper-V checkpoint merging in Windows Server 2016 Technical Preview 4. These two examples are pretty amazing and those results are driven by ReFS metadata operations as well.

Does it replace ODX?

While the results so far are impressive and I’m looking forward to more of this, it does not replace ODX. It complements it. But why would we want that you might ask, as we’ve seen in some early testing that it seems to beat ODX in speed? It’s high time to take a look at ReFS vNext Block Cloning and ODX in Windows Server 2016 TPv4.

The reality is that sometimes you’ll probably don’t want ODX to be used as the capabilities of ReFS vNext will provide for better (faster) results. But sometimes ReFS vNext cannot do this. When? Block cloning for all practical purposes works within a volume. That means can only do its magic with data living on the same volume. So when you copy data between two volumes on the same LUN or between volumes on a different LUNs you will not see those speed improvements. So for deploying templates stored on another LUN/CSV fast it’s not that useful. Likewise, if for space issues or performance issues you were storing your checkpoints on a different LUN you will not see the benefits of ReFS vNext block cloning when merging those checkpoints. So you will have to revise certain design and deployment decisions you made in the past. Sometimes you can do this, sometime you can’t. But as ODX works at the array level (or beyond in certain federated systems) you can get excellent speeds wile copying data between volumes / LUNs on the same server, between volumes / LUNs on different servers. You can also leverage SMB 3.0 to have ODX kick in when it makes sense to avoid senseless data copies etc. So ODX has its own strengths and benefits ReFS vNext cannot touch and vice versa. But they complement each other beautifully.

So as ReFS vNext demonstrates ODX like behavior, often outperforming ODX, you cannot just compare those two head on. They have their own strengths. Just remember and realize that ReFS vNext actually does support ODX so when it’s applicable it can be leveraged. That’s one thing I did not understand form the start. This is beginning to sound like an ideal world where ReFS vNext shines whenever its features are the better choice while it can leverage the strengths of ODX – if the underlying storage array provides it – for those scenarios where ReFS vNext cannot do its magic as described above.

The Future

I’m not the architect at Microsoft working on ReFS vNext. I do know however, that a bunch of very smart people is working on that file system. They see, hear and listen to our experiments, results, and requests. ReFS is getting a lot of renewed attention in Windows Server 2016 as the preferred file system for Storage Space Direct and as such for CSVs. Hyper-V is clearly very much on board with leveraging the capabilities of ReFS vNext. The excellent results of that, which we can see in speeding up VHDX creation/ extending and checkpoint merges, are testimony to this. So I’m guessing this file system is far from done and is going places. I’m expecting more and more workloads to start leveraging the ReFS vNext capabilities. I can see ReFS itself also become more and more feature complete and for example Microsoft has now stated that they are working on deduplication for ReFS, although they do not yet have any specifics on release plans. It makes sense that they are doing this. To me, a more feature complete ReFS being leveraged in ever more uses cases is the way forward. For now, we’ll have to wait and see what the future holds but I am positive albeit a bit impatient. As always I’m providing Microsoft with my feedback and wishes. If and when they make sense and are feasible they probably have them on their roadmap or I might give them an idea for a better product, which is good for me as a customer or partner.