Continuous available general purpose file shares & ReFSv3 provide high available backup targets


In our previous two blog posts on Veeam and SMB 3 we’ve seen how and when Veeam Backup & Replication can leverage SMB Multichannel and SMB Direct. See Veeam Backup & Replication leverages SMB Multichannel and Veeam Backup & Replication Preferred Subnet & SMB Multichannel.The benefits of this are more bandwidth, high availability, better throughput and with RDMA low latency and CPU offload. What’s not to like, right? In a world where the compute and networks need keeps rising due to the storage capabilities (flash storage) pushing the limits this is all very welcome.

We have also seen earlier that Veeam B & R 9.5 leverages ReFSv3 in Windows Server 2016. This provides clear and present benefits in regards to space efficiencies and speed with many backup file related operations. Read Veeam Leads the way by leveraging ReFSv3 capabilities

When it comes to ReFSv3 in Windows Server 2016 most of the focus has gone to solutions based around Storage Spaces Direct (S2D). That’s a great solution and it is the poster child use case of these technologies.

But what other options do you have out there to build efficient and effective high available backup targets creatively except for S2D? What if you would like to repurpose existing hardware to build those? Let’s take a look together at how continuous available general purpose file shares & ReFSv3v3 provide high available backup targets

CSV, S2D, ReFSv3 & Archival Data

In Windows Server 2016, traditional shared storage (iSCSI, FC, Shared SAS, Shared RAID) with CSV are not recommend to be used with ReFSv3. Why isn’t exactly clear. The biggest impact you’ll see is the performance difference when not writing to the owner node of the CSV in this use case. Even with a well configured RDMA network that difference is significant. But that doesn’t mean that the performance is bad. It’s just that many of the super-fast meta data operations are relatively and significantly slower when compared each other, not that any of these two are slow.


Microsoft does state that an S2D with ReFSv3 and SOFS shares can be used for archival data. Storage spaces and ReFSv3 also have the benefit of offering automatic repair of corrupt data from a redundant copy on the fly even when needed. So yes, the best know supported scenario is this one.

Continuous available general purpose file shares and ReFSv3 provide high available backup targets

But what if we need a high available backup target and would love to leverage ReFSv3 with Veeam Backup & Replication 9.5? Well, you can have 95% of your cookie and eat it to. All this without ignoring the cautions offered.

We could set up SOFS shares on a Windows Server 2016 Cluster with ReFSv3 with traditional shared storage. Some storage vendors do state this is supported actually.

That only means you don’t have the auto repair functionality ReFSv3 combined with storage spaces offers. But perhaps you want to avoid the risk of using ReFSv3 with CSV in a non S2D scenario all together. What you could do is forgo ReFSv3 and use NTFS. How well this will work for archival data or backup is something you’ll need to test and find out how well this holds up. There is not much info is out there, only other cautions and warnings that might keep you up at night.

There is another scenario however and that is using Windows Server 2016 failover clustering to set up continuously available general purpose file shares that leverage SMB3 transparent failover.

The good news is that general purpose file shares (no CSV) do work consistently with ReFSv3 because such a share/LUN is only exposed on one cluster node at the time, the owner. By having multiple shares and setting preferred owners we can load balance the workload across all cluster nodes.

Thank to continuous availability for general file shares and SMB 3 transparent failover we can still get a high available backup target this way. The failover is fast enough to make this happen and all we see with Veeam Backup & Replication is a short pause in throughput before it resumes after failover. To put the icing on the cake, you can leverage SMB multichannel SMB Direct for both backup and restores.

I would take a sizeable whitepaper to walk through the setup so instead I’ll show you a a quick video of a POC we did in the lab here


If you want to learn more come to the community & other conferences I’m speaking at and will be around for Ask The Experts time opportunities. I’ll be at the German Hyper-V community meet up, The Cloud & Datacenter Conference in Germany 2017, Dell EMC World 2017 and last but not least VeeamON 2017 (see  May 2017 will be a travelling month). 


What do you lose?

Potentially there is one big loss in regards to the capabilities of ReFSv3 with this solution when you are not using storage spaces. This is that you lose the capability to automatic repair of corrupt data. The ability of ReFSv3 to do so is tied into the redundant copies of Storage Spaces (parity/mirror).

What do you get?

That’s fine, the strength of this design is that you get the speed and space efficiencies of ReFSv3and high available backup targets in way more scenarios than “just” S2D. After all, not everyone is in a position to choose their storage fabric for backup targets green field or at will. But they might be able to leverage existing storage and opt to use SMB 3 for their data transport.

So even if you can’t have it all, you can still build very good solutions. It offers ReFSv3 benefits and high availability for your backup target via transparent failover with SMB transparent failover on continuous available general purpose file shares. This also only requires Windows Server 2016 Standard Edition, which is a cost saving. You get to leverage SMB Multichannel and SMB Direct. All this while not ignoring the cautions of using ReFSv3 in certain scenarios.

On top of that, if you use NTFS with this approach it will also work for Windows Server 2012 (R2) as the OS for the backup target cluster hosts.


I do not work for or at Microsoft, nor am I perfect or infallible just because I’m an MVP. You’ll have to do your own testing and validation. From our testing and without ReFSv3 bugs ruining the show, to me this is a very valid and cost effective approach.

Hyper-V Amigos Showcast Episode 12–ReFS v3.1 and Backup

In this Episode Carsten and I look at a single host deployment with Storage Spaces on Windows Server 2016. We create a “Hybrid” disk just like in Storage Spaces Direct by combining SSD & HDD in a storage Tier. We were very happy to discover that ReFSv3.1 does real time tiering.


We’re very excited about this because we want to leverage the benefits if Veeam Backup & Replication 9.5 brings by leveraging ReFSv3.1 (Block Cloning) in regards to backup transformation actions and Grandfather-Father-Son (GFS) spaces savings. To do so we’re looking at our options to get these benefits and capabilities leveraging affordable yet performant storage for our backup targets. S2D is one such option but might be cost prohibitive or overkill in certain environments.

ReFS v3.1 on non-clustered Windows Server 2016 hosts bring us integrity streaming, file corruption repair with instant recovery as protection against bit rot, the performance of tiered storage and SMB3 as a backup target at a great price point.

We encourage you to watch the video and see for yourself. As always, we had fun and hope your can learn something together with us, the Hyper-V Amigos Smile

Veeam Leads the way by leveraging ReFS v3 capabilities


You might have noticed that I’m pretty impressed by what Microsoft is doing with ReFS v3 in Windows Server 2016. You can read some of my musing on it in ReFS vNext Block Cloning and ODX and take a look at a comparison between ReFS & ODX speeds when creating VHDX files in Lightning Fast Fixed VHDX File Creation Speed With ReFS on Windows Server 2016 .

Note that this is also leveraged for accelerated checkpoint merges, VHDX resizing etc.

Now it goes without saying that Hyper-V (they’re the tip of the spear at MSFT) and other Microsoft products would take advantage of the capabilities of ReFS. But now we know that Veeam Backup & Replication 9.5 has made use of ReFS to help with the resilience of their backups, the speed of their Synthetic Full backups and the space required.


To a Hyper-V MVP and a Veeam vanguard it was obvious these two combined just had to lead to way for others to follow.

Veeam Leads the way by leveraging ReFS v3 capabilities

Veeam Backup & Replication 9.5 will leverage ReFS v3 …



and by doing so they deliver the following benefits:

  • Shorted backup windows and a reduced backup storage load on the repository
  • Reduced backup target storage capacity which is reducing or eliminating the need for deduplication in many scenarios.
  • Better backup data protection by leveraging the ReFS native capabilities to protect against bit rot which was one of the prime goals for which Microsoft designed ReFS.

How is this done?

ReFS v3 has “fast cloning” technology which Veeam is leveraging. This results in up to 10 times  faster creation and transformation of synthetic full backup files!  ReFS fast cloning allows for creating new files without physically moving data blocks between files. This is what delivers even shorter backup windows and lower backup storage load on the repository or repositories.

They use what they call “Spaceless full backup technology” which allows multiple full backup files to reside on the same ReFS volume that share the same physical data blocks. As a result they need less storage capacity which can reduce or eliminate the need (and cost) of deduplication appliances whilst leveraging commodity storage.

Lest see how this is done. A “legacy” full backup is created an consumes 30% storage capacity. Then we make incremental backups.


3 incremental backups add 3 * 10% of delta to the needed backup storage capacity which adds up to 60%.


We create a synthetic full backup and the copies of the data require another 30% of space (90%). 


No let’s compare this to v9.5 that leverages a Windows Server 2016 ReFS formatted backup target repository. Instead of copying data ReFS references already existing data block for a new file. This saves on IO, space and time!


Is this safe? What if those data blocks that are reference multiple times are corrupted? Well Veeam does have protection against that in place already! But it goes the extra mile as ReFS has the capabilities to protect against that itself or it’s power would also become its biggest weakness.

Veeam’s data integrity streams integration leverages ReFS data integrity scanner and even proactive error correction when used in combination with Storage Spaces to protect backup files from bit rot and allows for more reliable forever-incremental archiving. This helps make the spaceless full backup technology trustworthy & safe alongside the health checking & error fixing capabilities already available in Veeam Backup & Replication.


I’m impressed by the forward looking and fast adoption of the capabilities of ReFS v3 by Veeam and I’m testing Backup & Replication v9.5 Beta today in the lab. They have more up their sleeve by the way as they have some interesting work with PowerShell Direct to make backups ever more resilient in ever more scenarios. More on that later.

Anyone who said Veeam would lose its edge in the world of Hyper-V backups when Microsoft introduced their own native change block tracking (resilient change tracking) has clearly never dealt with Veeam seriously and professionally. I have and I’m always happy to chat to them as they have serious technical skills combined with vision and business acumen that makes sure they’re leaders in the business of backup. It makes me proud to be a Veeam vanguard and a MVP with a specialization in Hyper-V.

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


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.


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.


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.


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.