Category Archives: Storage

ReFS Supported Deployment Scenarios Updated

Posted on by
20

Introduction

Some support statements for ReFS have been updated recently. These reflect well over a year of me, fellow MVPs and others testing and providing feedback to Microsoft. For all practical purposes I’m talking about ReFSv3, which was introduced with Windows Server 2016. Read up on this because that’s what I’m discussing here: Resilient File System (ReFS) overview

As many you know the ReFS supported storage deployment option has “fluctuated a bit. It was t limited ReFS to Storage Spaces and standalone disks only. That meant no RAID controllers, no FC or iSCSI LUNs via a SAN whether that was a high end one or and entry level one that you normally only use for backup purposes.

I was never really satisfied with the reasons why and I kept being a passionate advocate for a decent explanation as tying a files system with the capabilities and potential of ReFS to almost a single storage solution (S2D, and yes that’s a very good HCI offering) isn’t going to help proliferate the goodness of ReFS around the globe.

I was not alone and many others, amongst them fellow MVPs Anton Gostev (Senior Vice President, Product Management at Veaam and an industry heavy weight when it comes to credibility and technical skill), Cars ten Rachfahl and Jan Kappen (both at Rachfahl IT-Solutions) were arguing he case for broader ReFS support. Last week we go the news that the ReFS deployment documentation had been revised. Guest what? Progress! A big thank you to Andrew Hansen for taking the time to hear us plead or case, listen to our testing results and passionate feedback. He picked up the ball, ran with it and delivered! Let’s take a look.

ReFS Storage Deployment Options

Storage Spaces Direct

Deploying ReFS on Storage Spaces Direct is recommended for virtualized workloads or network-attached storage. This is well known and is used for a Hyper Converged Infrastructure and Converged (SOFS) solution (Hyper-V, IIS, SQL, User Profile Disks and even archival or backup targets). You can deploy it with simple, mirrored (2-way or 3-way), parity or Mirror accelerated parity volumes.

Storage Spaces

Storage Spaces supports local non-removable direct-attached via BusTypes SATA, SAS, NVME, or attached via HBA (aka RAID controller in pass-through mode). You can deploy it with simple, mirrored (2-way or 3-way) or parity volumes. Do note that this can be both non-shared as shared storage spaces (Shared SAS enclosures). This is the high available solution with storage spaces we have before Windows Server 2016 added S2D.

Basic disks

Deploying ReFS on basic disks is best suited for applications that implement their own software resiliency and availability solutions. Applications that introduce their own resiliency and availability software solutions can leverage integrity-streams, block-cloning, and the ability to scale and support large data sets. A poster child for this use case is and Exchange DAG.

Now it is important to note that basic disks with ReFS are supported with local non-removable direct-attached disks via BusTypes SATA, SAS, NVME, or RAID. So yes, you can have RAID 1, 5,6,10 and make the storage redundant. Now, be smart, ReFS is great but it is not magic. If your workload requires redundancy and high availability you should provide it. This is not different when you use NTFS. When you have shared PCI RAID controllers (which can be redundant like in a DELL VRTX) this can be uses as well to create high availability deployments with shared storage.

SAN Storage

You can also use ReFS with a SAN over FC or iSCSI, normally those are always configured with some form of storage redundancy. You can consume the ReFS SAN storage on stand alone, member or clustered serves for high availability. As long as you use that storage for supported use cases. For example, it is and remains not support to put knowledge worker data on SOFS shares, not matter what the underlying storage for ReFS or NTFS volumes is. For backups this can leveraged to build some very capable solutions.

What were the concerns that made ReFS Support so limited at a given point in time?

Well one of them was confusion and concerns around how data gets flushed and persisted with non-storage spaces and simple disks. A valid concern but one you have with any file system so any storage array or controller needs to handle this well. As it turns out any decent piece of storage hardware/controller that’s on the Microsoft Hardware Compatibility List and is certified does its job well enough to guarantee this happens correctly. So, any certified OEM SAN, both entry level ones to high end enterprise grade gear is supported. Just like any good (certified) raid controller. Those are backed with battery backed caches that can survive down time for days to many weeks. You just pick the one that fits your needs, use case and budget form the options you have. That can be S2D, a SAN, a raid controller, or even basic directly attached disks.

My take on things

Why do I like the new supported options? Well because I have been testing them for backup targets, both high available one as non- high available one. I can have the benefits of ReFS that can be leveraged by backup software (Veeam Backup & Replication 9.5 for example) and have better performance, data protection with more type of storage than S2D. I like to have options and choices when designing as solution.

It is important to note one thing when you do not use ReFS in combination with Storage Spaces (S2D, Shared storage Spaces or “stand alone” storage spaces) with any form of data redundancy (2-way or 3-way mirror, parity, mirror accelerate parity). You will not have the built-in capability to repair data corruption than can occur while data sits on disk (bit rot) by leveraging the redundant copies in storage Spaces. That only comes when ReFS is combined with redundant Storage Spaces. Not with Simple Storage Spaces or any other storage array, redundant or not. The combination of ReFS with Storage Spaces offers this capability and is one of its selling points.

Other than that, the above ReFS storage deployment options let you leverage the benefits ReFS has to offer and yes, for some use case that will be preferred over NTFS. But don’t think NTFS should now only be used for the OS and such. That’s not the case. It is and remains very much the dominant file system for Windows. It’s just that now we get to leverage the goodness of ReFS for suitable scenarios with a lot more storage deployment options. This has a reason. For example, if you are going to do Hyper-V with a SAN the supported file system is NTFS, not ReFS. Mind you ReFS works but it’s not supported. I have tested this and while it works one of the concerns is the redirect IO traffic this incurs. With S2D the network fabric to deal with this is there by design: SMB Direct (RDMA) over 10Gbps or better. With a SAN that’s not necessarily so and as a result the network leveraged by CSV traffic might take a beating. The network traffic behavioral patterns are also different with ReFS versus NTFS on SAN based CSV than what you are used to with NFTS when it comes to owner and non-owner nodes. While I can make things work I must consider the benefits versus the risk of being unsupported. On a good SAN with ODX support that’s not worth the risk. Might this ever change? Maybe, but for now that’s it.

That said, when I design my ReFS LUNs and fabric well with a SAN and use them for a supported uses case like backup targets I am supported and I get to leverage the benefits of ReFS as it fits the use case very well (DPM, Veeam).

A side note on mirror accelerated parity

Mirror accelerated parity is only supported with S2D. That’s the only thing that, in regards to backup an archive targets that I want to keep testing (see Hyper-V Amigos Showcast Episode 12 – ReFS and Backup )and asking Microsoft to support at least on non-shared Storage spaces. I know shared storage spaces is being depreciated, no worries. That would make for some great, budget, archival and backup targets due to the fact you get bit rot protection due to the combination ReFS with redundant Storage Spaces. I even have some ideas on how to add tuning capabilities to the mirror / parity movement of data based on data age etc. I can dream right ?

Conclusion

To all the naysayers, the ones that bashed me when I discussed options for and the potential for ReFSv3 outside of S2D, take note, this is where we are today.

clip_image001

And I like it. I like the options ReFSv3 offers with variety of storage solutions to design and implement backup targets for many different needs and budgets. That’s what I like as I’m convinced that one size fits all solution are an illusion. Even at economies of scale and with commodity materials understanding the context in which to design and implement a solution matters, as it allows you to chose the proper methods for the given needs when you genuinely understand the challenge.

If you need help with this there are quite a number of highly skilled, experienced people with the right mindset to make help you maximize your ROI and TCO in an effective and efficient way. Many of these are MVPs and have their own business or work for IT firms where customers are not milked like cattle but really do provide high value services. Just reach out.

Storage Migration Service or MSFT adds WorkingHardInIT like skills in Windows Server 2019

Posted on by
Reply

As readers of my blog will know very well is that one of my track records is that I’m fairly successful in keeping technology debt low. One of the workloads I have always moved successfully over the years are file servers. Right now, almost all, almost everywhere, are the goodness of SMB3 and are high available clustered file server roles. You can read about some of those efforts in some of my blogs:

Sometimes this cans quite a challenge but over the years I have gained the experience and expertise to deal with such projects. Not everyone is in that position. This leads to aging file services, technology debt, security risks, missed opportunities (SMB3 people!) and often even unsupported situations in regards to hardware and software. While since the release of Windows Server 2016 this image has shifted a bit, you can clearly see the pretty depressing state of file services. Windows rules the on premises server world but the OS versions are aging fast.

clip_image002

Image courtesy of SpiceWorks: Server Virtualization and OS Trends

The operating systems are ancient, old or aging and we all know what this means in regards to the SMB version in use.

Now I work hard, effective and efficiently but I cannot be everywhere. Luckily for you Microsoft has a great new capability coming up in Windows Server 2019, the Windows Server Storage Migration Service.

clip_image004

Figure2: the WorkingHardInIT feature officially known as the Windows Server Storage Migration Service. Image courtesy of Microsoft.

Thanks to Ned Pyle and his team’s efforts you can no aspire to me as successful as me when it comes to migrating file services to newer environments. It’s like having WorkingHardInIT in a Windows feature. Isn’t that cool?! If they sold that separately they would make a pretty penny but they luckily for you include it with their new server OS version.

Storage Migration Servers deals with many of the usual problems and intricacies of a storage / file service migration. It will handle things like share settings, security settings, network addresses and names, local accounts, encrypted data, files that are in use etc. To handle you project you have a GUI and PowerShell automation at your disposal. Windows Server 2019 is still being perfected and you can still provide feedback while testing this feature.

Things to note for now (bar the requirements for testing as described in Ned Pyle’s blog) are:

Supported source operating systems VM or hardware (to migrate from):

  • Windows Server 2003
  • Windows Server 2008
  • Windows Server 2008 R2
  • Windows Server 2012
  • Windows Server 2012 R2
  • Windows Server 2016
  • Windows Server 2019 Preview

Supported destination operating system VM or hardware (to migrate to):

  • Windows Server 2019 Preview*

* Technically your destination for migration can be any Windows Server OS, but we aren’t testing that currently. And when we release the faster and more efficient target proxy system in a few weeks it will only run on Windows Server 2019.

In my humble opinion that almost has to be Storage Replica technology being leveraged. Something that has been proven to be very much more efficient that copying files. Microsoft already promotes Storage Replica to other server or itself as a way of moving data to a new LUN.

Anyway, this is a cool feature that should grab your attention. Thank you Ned Pyle and team! And while you’re busy putting this great capability into Windows Server 2019 (Standard and Datacenter) consider doing the same for full featured Storage Replica in Windows Server 2019 Standard .

It’s not as simple as renaming the avhdx to vhdx

Posted on by
1

This arrives in via the feedback option on my blog

Hi. I see through your website that you are an expert in vhdx / avhdx file. I had a system crash with data loss. I think this data is in an avhdx file. When I rename this file in vhdx, I can mount it but I have an error: the file is corrupted. Do you know a procedure to repair this type of file? I thank you in advance for your support!

Oh dear! An expert? While flattery can get you a long way in life with certain people virtual disks are impervious to that sort of thing. Look, MVP, Veeam Vanguard, Dell Rockstar … tip of the spear, edge of the sword, it’s all fine and well but it’s no good to split a granite piece of rock and virtual disks don’t care about titles, jut about how they are designed to work.

Before we dive into some more details please use the comments sections under the relevant blog post to ask questions. That way everyone can benefit form the answer. It’s all quite anonymous if you want it to be. Secondly vendors like Microsoft have great public support forums with many thousand pairs of eyes reading. That might also work better and faster for your needs.

Some details

When you have avhdx your data is stored in the avhdx and in the parent disks (more avhdx but at least always one vhdx). While you can throw away what’s in a avhdx under certain conditions (and lose that data) and mount the vhdx you cannot throw away the vhdx and hope to be able to access the data in the avhdx you rename to vhdx.

clip_image002

For a case of real data corruption, not just phantom or mixed up VHDX/AVHDX chain, where you can try to intervene, even manually if needed – and if you have the skills – you’ll have to recover or restore data.

If the storage on which the vhdx/avhdx reside is corrupted a good but time-consuming run of chksdk /f /r can do the job. I have done that before with success. But there are no guarantees in this game.

Other than that, or when the storage is gone, it is restore time. This can be leveraging whatever backup solution you use or VSS snapshots on the storage side of things. Those options are your best bet. You can find some more info on manually manipulating vhdx/avhdx files here but that’s not what you’re facing here it seems.

If you don’t have recovery options in place, what can I say?

Stop what you’re doing and contact a good data recovery company. Only damage can come from trying if you don’t know what you’re doing. You can hope trial and error will fix it but that would be the triumph of hope over experience. You’re usually not that lucky. Trust me.

The snarky bit

I’ll fight like hell if I’m in a pickle and the data is valuable. But it’s near to impossible to do it for someone else as it’s hard, time consuming and often it’s a case were the files have been worked on before, so they tend to be messed up. If the data is not that valuable, just eat the loss.

In reality my time always seems less valuable then peoples their data . Now if you say you can help me retire early by trying anyway and are OK with a best effort, no guarantees given deal I might do it. But I’m pretty sure investing in backups and restores is way cheaper and will lead to better results. Your data is important and valuable, even when my time is not. Just saying

Latency kills

Posted on by
2

Introduction

I was investigating a very problematic Windows Server 2016 Hyper-V cluster. That cluster was just performing horribly. “Everything” was hanging, stalling, crashing and RHS.exe errors where flying around while WER dumps got created by the dozen. Things were extremely slow up to the points functionality was just failing. The “fun” thing was that the cluster validation wizard while slow gave that cluster a big thumb up and a supported status as all was well.

Prying around

Time to pry around a bit and see if we could find something wrong. We save live migrations stall, fail, last forever in pending or get stuck at a certain percentage, sometimes finally succeeding with ridiculous blackout times. We could not open up virtual machine properties or very slowly. The FCI GUI was highly unresponsive but so was the Hyper-V Manager GUI or even PowerShell. Those were hanging at even loading the virtual machines or enumerating them with Get-VM. Everything was slow to the point it timed out or crashed. Restarting the services (Cluster, Hyper-V) didn’t do anything and restarting VMMS was super slow or just got stuck. It was a depressing sight for which people tended to blame Hyper-V / Microsoft.

As the title gives away it was latency. Not just ordinary high latency. Real bad latency. That kind of latency kills. Extreme latency produces symptoms that are similar to bugs or corrupt components of roles and features. We have a tendency to look at those first in the event logs and then we look at the network and its usual suspects (VMQ, SET, DCB). But nothing pointed to an issue that I could find.

So, storage maybe?Well we did find one Hyper-V host in the cluster with one HBA port producing too many error so we disabled that FC port for testing. No joy the Hyper-V cluster after a clean reboot of all nodes remained problematic. So on to the storage array itself.

Well holy smoke! On the two volumes for CSV in those cluster we saw latencies that were so bad I could not even believe a single VM would boot. It actually made my appreciation for Hyper-V and clustering grow as it managed to do at least a couple of things. With such latencies I would expect the services to just crash & call it a day.

clip_image002

The horrific latency on one of the CSV LUNs.

Looking at the logs we saw that the latencies occurred on the FC HBAs of the controllers. Each one above 50ms, peaking to 150-250ms and one huge peak at almost 500ms. We saw this on all four HBA’s.

clip_image004

The latency on one of the 4 FC HBA’s on one of the controllers. Not a good day. All HBAs had high latencies like this.

The issues were not at the host level (host HBA’s) or not even at the IOPS/bandwidth level of the storage itself. The latency for some reason was spiking. Further investigation lead to the conclusion that the issue was related to synchronous replication going totally wrong. Moving the replication mode to asynchronous fixed that. We’re now investigating why this happened and how to prevent this from happening again. But that’s another story.

clip_image006

Latency on one of the 4 FC HBAs on one of the controllers after we fixed the issue.

Do not assume anything

So, there you go. Everything depends on everything in some direct or indirect way. It’s all connected and that my friends, is why I’m a proponent of “service resilience engineering” where the responsible team owns the entire stack. That’s is how you can act fast.