Microsoft Storage Spaces Direct added to Evaluator Group Research

By Eric Slack, Tuesday, September 5th 2017

Categories: Analyst Blogs

Tags: blog, checkbox, Eric Slack, Evaluator Group, Microsoft, storage spaces direct,

Plus updates to HCI and SDS products



Evaluator Group recently updated the Evaluator Series Research coverage for several Hyperconverged Infrastructure (HCI) appliance products, which we’ll go over in this blog. We also added Microsoft Storage Spaces Direct (S2D) to the software defined storage product category, releasing a Product Brief and including S2D in the Open Storage Platform Comparison Matrix.

What is Storage Spaces Direct?

Storage Spaces Direct is software-defined storage that runs in the Windows Server 2016 kernel, clustering Windows servers in a choice two different configurations, a scale-out storage system or an HCI using Hyper-V. In “Converged” mode, storage and compute are run on separate servers, allowing S2D to virtualize local storage capacity on storage nodes into a common pool which can be connected to compute nodes. This disaggregated architecture also allows the cluster to scale capacity separately from compute. In “Hyper-converged” mode the compute and storage functions are combined into the same nodes, which are sold by Microsoft partners as an HCI appliance.

How it works

S2D essentially takes Storage Spaces, a volume management service from Windows Server 2016 R2, and adds the ability to cluster disks in multiple servers, creating a common storage pool. It uses a technology called Software Storage Bus (SSB) that allows each node to see all storage devices (drives on the other nodes) in a “mesh” topology. S2D implements a mirroring or parity scheme using this common drive pool across all nodes.

Microsoft has developed the new Resilient File System (ReFS) which has been optimized for virtual workloads and designed to replace NTFS in Hyper-V deployments. SSB also implements a per-node caching mechanism called Storage Bus Cache (SBC) that optimizes performance for servers that have multiple types of storage devices, typically NVMe SSD and SATA SSD or SATA SSD and HDD.

What’s different from other HCI/SDS Technologies?

Cost – Like VMware’s vSAN, S2D runs in the OS kernel, but is not a for-charge option with Windows Server 2016, which can lower its effective cost.

Performance – S2D uses SMB as the transport layer between nodes, with SMB Direct providing RDMA connectivity, which can dramatically lower network latency compared with the Ethernet connectivity that other SDS and HCI products use.

Scaling Flexibility – S2D’s disaggregated architecture allows compute or storage nodes to be added independently, or both functions can be run on the same nodes.

Windows-only – Virtual server environments must be Hyper-V and all nodes must be Windows servers.

Evaluator Group Comments

Storage Spaces Direct has some significant technical advantages over other SDS technologies, especially its performance and flexible architecture, advantages that are most applicable to larger deployments. With the rise of all-flash nodes, the push towards RDMA and the scaling challenges that many HCIs have, S2D would seem like an ideal technology for these products.

But given VMware’s dominance of the hypervisor market, (72% of respondents in our 2016 “HCI in the Enterprise” study used VMware compared with 11% that used Hyper-V), we don’t see S2D becoming a serious HCI alternative in the enterprise. However, in the SMB space, where Microsoft has a bigger presence, S2D is a stronger solution.

S2D’s disaggregated architecture does allow it to become a software-defined storage solution with a scale-out Windows file system. But without the ability to do NFS or block storage, S2D is limited as a stand-alone, scale-out storage solution.

Scale Computing

Scale Computing has added an all-flash node and increased the capacity of its existing lineup. The Product Brief and HCI Comparison Matrix have been updated to reflect these and several other changes. While firmly focused on the SMB market, Scale is also seeing some success in large enterprises with remote offices that need a cost-effective HCI solution.


vSAN v6.6 was released earlier this year, adding cluster-level encryption, local mirroring in stretched clusters, performance and manageability upgrades, plus a number of other enhancements. vSAN is the SDS storage layer in the VxRail HCI product from Dell EMC. But VMware actually sells three times as many vSAN licenses through its Ready Nodes program. Each of the OEM vendor partners, which now number 15, offers multiple server configurations, all certified to run with vSAN.


Pivot3 acquired NexGen a couple years ago and has now completed the integration of NexGen’s PCIe flash and advanced QoS technologies, which were included in Pivot3’s new Acuity software platform. This product has a new architecture using Accelerator Nodes to incorporate the QoS-controlled PCIe flash layer into the Pivot3 HCI appliances, plus enhanced performance and management.

Cisco HyperFlex

Cisco released a new “Edge” configuration, a 3-node cluster of the HX220 1U appliances that’s designed to lower the cost for small and remote environments. It has a 3 drive minimum, a single CPU option and doesn’t require fabric interconnects (all other HX clusters come with a top-of-rack switch). The company also upgraded the performance and efficiency of their SpringPath software, compared with the previous version.

The amount and diversity of technology available in infrastructure products can be overwhelming for those trying to evaluate appropriate solutions. In this blog we discuss pertinent topics to help IT professionals think outside the checkbox of features and functionality.

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