Microsoft Windows Server 2016 offers a tremendously expanded set of features across the board vs previous versions of the hypervisor.

Microsoft has made great strides in achieving more feature parity with other major players such as VMware.

One of the powerful new features in Windows Server 2016 is the introduction of Storage Spaces Direct (S2D) software defined storage solution which is a direct competitor with VMware’s vSAN solution. Storage Spaces Direct is a very performant, scalable, and efficient storage platform.

How do customers choose between Hyper-V Storage Spaces Direct and the traditional SAN configuration when provisioning storage for a Windows Server 2016 Hyper-V cluster?

What are the use cases, advantages, and disadvantages of both Storage Spaces Direct and traditional SAN storage?

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Read on to know the answers!

What is Windows Server 2016 Storage Spaces Direct?

Windows Server Storage Spaces Direct was introduced with Windows Server 2016. Again, drawing a comparison here with VMware vSAN that many are familiar with, Storage Spaces Direct works on similar hardware architecture ideas.

With Storage Spaces Direct, locally attached drives are used to create software-defined storage in a converged or hyper-converged manner. It includes creating storage tiers including caching and capacity tiers.

Using erasure coding, Storage Spaces Direct is able to provide fault tolerance between nodes. Converged networking utilizing RDMA is also able to deliver very good network performance.

What are the requirements for Storage Spaces Direct?

There are several requirements for configuring Storage Spaces Direct across both the physical server hardware and operating system version.

Windows Server 2016 Storage Spaces Direct Requirements

There are quite a few hardware considerations to be made when considering Windows Server 2016 Storage Spaces Direct. The following are requirements for building out compatible hardware for Windows Server 2016 Storage Spaces Direct.

Windows Server 2016 Certified

Hardware needs to be certified to run on Microsoft Windows Server 2016. A great resource for testing whether or not specific hardware is tested and approved for use with Microsoft Windows Server 2016 is the Windows Server Catalog.

Windows Server Catalog allows seeing if specific hardware his certified

Physical Servers

  • Storage Spaces Direct needs a minimum of (2) servers and can contain a maximum of (16) servers
  • It is best practice to use the same make/model of servers


  • Intel/AMD procs – Nehalem/EPYC or newer


  • You need enough memory for Windows Server 2016 itself
  • Recommended 4GB of memory for every 1 TB of cache drive capacity on each server


  • Any Windows supported boot device
  • RAID 1 mirror for boot drive is supported
  • 200 GB minimum boot drive size


  • (1) 10 Gbps network adapter per server
  • Recommended at least 2 NICs for redundancy
  • A (2) server configuration supports a “switchless” configuration with a direct cable connection


  • SATA, SAS, and NVMe supported
  • 512n, 512e, and 4K native drives all supported
  • SSDs need to have power loss protection
  • Direct attached SATA drives supported
  • Direct attached NVMe drives
  • It is not supported to have a RAID controller card or SAN storage. HBA cards must be configured in pass-through mode

Supported Drive configurations for Storage Spaces Direct (courtesy of Microsoft)

Windows Server 2016 Operating System Requirements

  • Windows Server 2016 Datacenter License is required for Storage Spaces Direct

Windows Server 2016 Storage Spaces Direct Architecture

Typically, in Hyper-V environments, you may want to utilize a hyper-converged solution. Storage Spaces Direct will automatically use the fastest storage (SSD or NVMe) for caching. The caching mechanism is dynamic, meaning it can change the drives that serve the caching mechanism due to changes in storage traffic or even an SSD failure.

Microsoft recommends at least (2) caching devices per node utilizing either SSD or NVMe drives. Microsoft also recommends making use of the new Resilient File System with the fast-cloning technology and resilient nature.

As far as fault tolerance, if you have three or more nodes in your cluster, Storage Spaces Direct is resilient to up to two drive losses or losing two hosts. With two-node clusters, the hit on disk space is quite high since the cluster utilizes a two-way mirroring mechanism for fault tolerance. This means you essentially lose 50% of your disk capacity.

When utilizing 4 node clusters and larger, you can take advantage of erasure coding similar to RAID 5 which is much more efficient from a capacity standpoint (60-80%).

However, this erasure coding is heavier on writes.

Microsoft has worked on this problem with Multi Resilient Volumes (MRVs) using ReFS. This creates a three-way mirror with erasure coding that acts as a sort of a write cache that works extremely well with Hyper-V virtual machines. Data is safely stored on three different drives on different servers.

Windows Server 2016 SAN vs Storage Spaces Direct

With the new age of software-defined storage and hyper-converged infrastructure capabilities supported in today’s hypervisors, the choice for storage today is not so clear-cut as it has been in years past.

Hyper-V administrators today with the new Storage Spaces Direct capabilities built inside of Hyper-V have the same question – stay with the familiar traditional SAN storage or utilize Storage Spaces Direct?

Both architectures will provide great platforms for Hyper-V virtual machines. Even though S2D is the new comer on the scene, it is already a very stable and reliable solution for running production workloads in a Hyper-V virtual environment.

However, there may be certain features or functionality, as well as use cases that may dictate one solution over the other. Let’s consider some potential characteristics of each solution that may help choose one over the other.

The comparison is as follows,

SAN based storage is tried and proven and most vendors today have Hyper-V compatible solutions. Storage Spaces technology has been in existence since Windows Server 2012 and not before.

Don’t think that just because you are using Windows Server 2016 Hyper-V that you must use Storage Spaces Direct. Oftentimes, procedures and processes are in place that organizations have used successfully with SAN storage in their virtualized environments that work very well and efficiently.

If you are comfortable with these process, procedures, and vendor solutions in your environment, this can certainly be a major reason to stick with SAN storage for Windows Server 2016 Hyper-V.

Storage Spaces Direct is also a great solution and often is much cheaper than high-end SAN storages from various vendors.

Additionally, the storage provisioning and management becomes part of the Windows Server 2016 operating system and not a separate entity that must be managed with disparate tooling and vendor utilizes.

Storage Spaces Direct can be fully managed and configured from within PowerShell which is certainly a trusted and powerful solution that is baked into today’s Windows Server OS.

Performance for many is a driving factor when it comes to choosing a storage solution. Can Storage Spaces Direct perform adequately for running production workloads? A published article from Microsoft shows Storage Spaces Direct enabled servers providing 60GB/sec in aggregate throughput using (4) Dell PowerEdge R730XD Servers. The solution can certainly perform and perform well!


Microsoft Windows Server 2016 Hyper-V has many great new features. With the introduction of Storage Spaces Direct in Windows Server 2016, Microsoft has become a major player in the realm of software defined storage.

Hyper-V administrators now have another great option when it comes to provisioning storage for production virtual machine workloads. With many options, there often comes the questions of which of those options to use in various use cases. Many Hyper-V administrators may wonder if using SAN storage is still the best option overall.

However, as shown, Storage Spaces Direct is already a tried and true platform for production Hyper-V workloads and administrators can use it confidently in their enterprise datacenters. There are reasons that one might choose one solution over another.

One of the reasons is the need for deduplication. Currently, Storage Spaces Direct does not support deduplication. There is no doubt that in future versions of Storage Spaces Direct, deduplication features will be included in the solution as well as other expanded storage functionality. There may be other advanced storage features that organizations may find that third-party SAN vendors support that Storage Spaces Direct does not support currently.

However, the ease of management and price point of Storage Spaces Direct makes it a very attractive solution for organizations today standing up new Hyper-V infrastructure. Additionally, performance is blazingly fast with Hyper-V Storage Spaces Direct.

Either way Windows Server 2016 Hyper-V offers the flexibility and options to suite the needs of organizations both today and tomorrow.

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