Storage Spaces Direct Explained – Applications & Performance

Applications

Microsoft SQL Server product group announced that SQL Server, either virtual or bare metal, is fully supported on Storage Spaces Direct. The Exchange Team did not have a clear endorsement for Exchange on S2D and clearly still prefers that Exchange is deployed on physical servers with local JBODs using Exchange Database Availability Groups or that customers simply move to O365.
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Performance

Microsoft showed all kinds of performance #s but these are using all NVMe SSD systems and real-world workloads like 100% 4k Random Reads.
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Much like VSAN, Storage Spaces is implemented in-kernel. Their messaging is very similar as well, claiming more efficient IO path, and CPU consumption typically way less than 10% of system CPU. Like VSAN, the exact overhead of S2D is difficult to measure.
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Microsoft is pushing NVMe Flash Devices for S2D and here are some examples of their positioning.
Their guidance was to avoid NVMe devices if your primary requirement is capacity as today you will pay a significant premium $/GB.
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Where NVMe shines is on reduced latency and increased performance with NVMe systems driving 3.4x more IOPs than a similar SATA SSD on S2D.
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There is also a significant benefit to CPU consumption with NVMe consuming nearly 50% less CPU than SATA SSDs on S2D.
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I also want to point out that the Azure Storage team is working very closely with Intel and Micron and will be moving parts of Azure to 3D Xpoint as soon as possible. This will filter down to S2D at some point, and we should expect them to be close to the bleeding edge for supporting new storage class memory technologies.
Scalability

Storage Spaces Direct will scale up to 16 nodes. In earlier Tech Preview releases they supported a minimum cluster size of 4 nodes. Recently they dropped that to 3 nodes and this week at Ignite they announced support for 2-node configurations. The 2-node configurations will use 2-way mirroring and require a separate witness that can be deployed on-premise or as a remote witness in Azure. Support for min 2 node configs does give them an advantage in ROBO and mid-market especially when low-cost is more important than high availability.

S2D will support both scale-up (adding additional local disk) and scale-out (with support for adding nodes in increments of 1).
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Product Positioning

Microsoft’s guidance is for customers to use smaller hyper-converged configurations for ROBO and small departmental workloads where cost efficiency is the primary driver. For larger enterprises and hosters/service providers, Microsoft recommends a converged model that allows the independent scaling of compute and storage resources.image043
So How Do Customers Buy Storage Spaces Direct?

Storage Spaces Direct is a feature of Windows Server 2016 and customers get it for free with DataCenter Edition. Customers will have the option of DIY or purchase one of the new Storage Spaces Direct reference architecture solutions from one of 12 different partners.
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With previous storage spaces offerings in Server 2012 and 2012R2, Microsoft put the technology out there for the DIY crowd and hoped that the server vendors would find the technology interesting enough to add to their portfolios. The problem was it needed JBOD shelves and in most server vendor organizations, JBODs fell under the storage teams, not the server teams. There was no way that any storage team was going to jeopardize their high margin traditional storage business by offering low margin Storage Spaces based JBOD solutions. Most vendors didn’t even want to sell JBODs at all. For example, Dell typically overpriced their JBODs to make EqualLogic look like a good deal at just a 15% uplift from a basic JBOD shelf…. much like movie theaters get us to buy the large popcorn for 50 cents more.

With Storage Spaces Direct, Microsoft is now dealing with the server part of these organizations… and all these guys care about is selling more servers. So Spaces went from having no partner interest to having support from all of the major server vendors.

However, since S2D is free with Windows and channel partners only get paid for the server sale, there is little incentive for them push S2D over other HCI options on these platforms. Therefore, I suspect that the majority of S2D adoption should come from customers asking to buy it rather than partners pushing it as an option.
So here is what the partner ecosystem looks like today.
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To formalize this, Microsoft created a new program called Windows Server Software Defined (WSSD) allowing partners to submit validated WSSD Reference Architectures. Microsoft provides the validation tools and methodology and the partner does the testing. They get a Windows Server 2016 Certified Logo plus SDDC Additional Qualifiers.
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Partners can offer their choice of Hyper-Converged or Converged configurations. Here’s where the classic Microsoft unnecessary complexity comes in… Within Hyper-Converged there are two additional options – Standard and Premium. Premium has some additional SDN and Security features turned on, but it’s simply a configuration thing. All of these come with Datacenter Edition so there is no cost or licensing difference.
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Here are a few examples of the offerings. S2D offerings will be available starting in mid-October as soon as Server 2016 goes GA.
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You may be asking who is responsible for support? Because it’s just a reference architecture, there is a split support model. Customers will call the server vendor for hardware issues and Microsoft for software issues.

Conclusions…

Storage Spaces has come a long way since Server 2012 and will be considered a viable option for customers looking at software-defined storage solutions. Some of the customers perceived advantages of S2D will be… low cost, min 2-node config, a broad choice of hardware vendors, storage QoS, NVMe support, single vendor software stack, and choice of deployment model (Hyper-Converged or Converged). Probably the most important of those is the price. Understanding the differences will be key. It’s tough to compete against ‘good enough’ and ‘free’.

Microsoft has not been very successful driving Storage Spaces adoption in the last 2 releases. Part of this is due to product immaturity, but most of this is because they didn’t build any real sales program around it. This hasn’t really changed with the WSSD Reference Architecture program. The big boys like Dell, HP, and Cisco are not going to position S2D over their own HCI offerings and the smaller players like SuperMicro, DataON and RAID Inc will never drive any significant adoption. Regardless of hardware platform, there is a very little incentive for the channel to sell S2D reference architectures over other HCI solutions (where they get paid for both the SW+HW sale). So without a strong sales program, I don’t believe that we will see S2D emerge as a big market share anytime soon.

Until next time, Rob.

Storage Spaces Direct Explained – ReFS, Multi-Tier Volumes and Erasure Coding

Here’s where we dive in and get dirty…but I promise by the end of my series, you will smiling like my friend here. I am planning a surprise with special guest bloggers. Stayed Tuned. Now one to the show…..
Storage Spaces Direct Explained ReFS

The NEW ReFS File System, Multi-Tier Volumes and Erasure Coding

Storage Spaces Direct Explained ReFSLike S2D, the ReFS file system actually isn’t new either, they have been working on it for several releases now also.  In Windows Server 2016, it finally drops the tech preview label and is now ready for production.  And there is a lot of benefits… like volume creation doesn’t have to zero out the volume for 10 minutes like NTFS. It’s just a metadata operation that is effectively instantaneous now, I’m just going to focus on the couple of benefits that ReFS has for S2D.
For those not familiar Erasure coding (EC) and to prepare you for the next part, EC is a method of data protection in which data is broken into fragments, expanded and encoded with redundant data pieces and stored across a set of different locations.
The original goal of EC was to enable data that becomes corrupted at some point in the storage process to be reconstructed by using information about the data that’s stored elsewhere.  Erasure codes are great, because of their ability to reduce the time and overhead required to reconstruct data. The drawback of erasure coding is that it can be more CPU-intensive, and that can translate into increased latency.
Now all that being said, classic erasure codes were designed and optimized more for communication, not for storage. Naively applying classic erasure codes in storage is okay, but is missing enormous efficiencies. Microsoft has developed their own erasure codes optimized for storage called Local Reconstruction Codes (LRC). I will cover this brieifly further down in the post.
Now back on to S2D…For data protection, S2D uses either 3-way mirroring or distributed parity with EC.  Mirroring gives you great write performance, but only 33% data efficiency.  EC gives you good data efficiency, but random write performance isn’t great for hot data.  ReFS supports the ability to combine different disk tiers using different parity schemes in the same vDisk. This allows S2D to do real-time data tiering by writing new data to the mirror tier and then automatically rotating cold data out to the parity tier and applying the erasure code on data rotation.
It is important to note that ReFS does not currently support Deduplication.  There was a question on this in every session and MSFT says that this is all the ReFS is currently focused on. So we’ll expect to see it land in ReFSv3. For now, customers can get dedupe with S2D by using NTFS. 🙁
Storage Spaces Direct Explained ReFS Storage Spaces Direct Explained ReFSNote if you only have two types of storage then the highest performing is used for the cache while the other type will be divided between performance and capacity with the different resiliency option (mirror vs parity) providing the performance/capacity difference between the tiers. If you only have one type of storage then the cache is disabled and the disks divided between performance and capacity like the previously mentioned case.
For non-Storage Spaces Direct only two tiers, of storage are supported like Windows Server 2012 R2, i.e. SSD and HDD, there is no cache. If you had NVMe storage that could be the “hot” tier while the rest of storage (SSD, HDD) could be the “cold” tier (you name the tiers whatever you want) but you cannot use three tiers.
Storage Spaces Direct Explained ReFS Storage Spaces Direct Explained ReFSStorage Spaces Direct Explained ReFSDuring Ignite 2016, Microsoft took many shots at VMware. Microsoft said that there’s a right way and a wrong way to do erasure coding.  “When you do it the wrong way, performance sucks and you have to limit it to all-flash configurations.”
Microsoft research is using a new technique called “Local Reconstruction Codes”. It uses smaller groups within the vDisk that allows them to recover from failures much faster by not having to reconstruct data from across the entire pool. This combined with multi-tier volumes gives S2D good performance, even on hybrid systems. Sounds like a technology that I seen before. Hmmm..I wonder where…….  😉
Storage Spaces Direct Explained ReFSOk, that’s all for now. next up, Fault Tolerance and Multisite Replication with S2D….

Until Next time, Rob….

The Evolution of S2D

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The intention of this blog post series is to give some history of how Microsoft Storage Spaces evolved to what it has become known today as Storages Spaces Direct (S2D). This first blog post will go into the history of Storage Spaces. Over my next few posts, I will delve further into the recent Storage Spaces Direct release with Windows 2016 server.  l will conclude my series with where I think it’s headed and how it compares to other HCI solutions in general. Now let’s go for a ride down memory lane….

The Evolution of Storage Spaces

Let me remind everyone, Storage Spaces isn’t new.  Microsoft has been working on it for over 6 years and it first shipped with Windows Server 2012.  Back then, Microsoft’s goal was to replace the components of a traditional SAN with software intelligence running on cheaper commodity hardware… much like everyone else was starting to do back then.
Their somewhat unique approach was to replace traditional expensive hardware storage controllers with lightweight servers running software controllers connected to shared JBOD disk shelves.  The software controllers were grouped together as a scale-out file server (2 or 4 controllers at that time) and presented an SMB storage target over a standard Ethernet network.  The storage was consumed by VMs running on Hyper-V hosts or by workloads running on physical servers.  Now do note at this time, they were still maintaining a 3-tier architecture with a disaggregated compute layer.  There was a reason for this.  Traditional storage network protocols can consume between 25-40% of system CPU to service IO.

To try to address this problem, Microsoft started making investments in SMB Direct (SMB over RDMA).  RDMA or Remote Direct Memory Access provides high network throughput with low latency while using significantly lower system CPU.  In Microsoft’s implementation, this allowed them to drive much higher VM densities on the compute layer and go very CPU light on the storage controller hardware.  A hyper-converged architecture didn’t make much sense for them at the time.

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Also, one of the limitations of this architecture was… it still used ‘shared storage’.  Because of that, they needed to use dual-ported SAS drives.  But at the time single port SATA drives were available in higher capacities and at a much lower cost.  Another factor at the time was that all the hyper-scale cloud providers were using SATA drives further driving the cost down.  All of these factors IMO forced Microsoft to dump the shared storage model and move to ‘shared nothing’ storage… which basically meant each storage controller had its own storage (local or in a direct attached JBOD) or ‘shared nothing’. Reminds me of an old saying in tech, If at first, you don’t succeed; call it version 1.0. 🙂

Fast Forward to Today

Storage Spaces with ‘shared nothing’ storage is now referred to as Storage Spaces Direct or S2D for short.  With Windows Server 2016, Storage Spaces Direct can now be deployed in either a more traditional disaggregated compute model or as a Hyperconverged model as shown below:
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As mentioned above, over the next few posts in this series, I will dive into the basics, ReFS with S2D, Multi-Tier Volumes, Erasure Coding, Fault Tolerance, Multisite Replication, Storage QOS, Networking,  Management, Native App Support, Performance claims, Scalability, Product Positioning, How to buy? and my final conclusions of S2D as it compares to other HCI solutions.

Until next time, Rob…