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Accelerated Erasure Coding Storage Spaces Direct introduces hybrid volumes, which is in 
addition to the existing mirror and erasure coding volume types. Hybrid volumes mixes the 
best of mirror (performance) with the best of erasure coding (efficiency) into a single volume 
with automatic real-time storage tiering. 
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Efficient VM check-points Storage Spaces Direct utilizes the new ReFSv2 file system, 
which when combined with Hyper-V can do very quick and efficient VM checkpoints with 
little overhead and storage I/O. 
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Scalability Storage Spaces Direct can scale from 2 to 16 servers. You can add servers as 
needed, and data can be rebalanced to best utilize the additional resources. Microsoft and 
Intel demonstrated a 16 server Storage Spaces Direct deployment using all NVMe SSDs at 
IDF 2015. 
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Health Service Storage Spaces Direct includes an intelligent built-in diagnostic engine 
that makes it possible for administrators with limited technical expertise to monitor and 
operate the system day to day. 
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The Health Service actively monitors the underlying cluster, storage hardware, and 
software-defined storage stack to detect problems and generate alerts that contain 
precise instructions for how to react. 
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Performance and capacity information is aggregated to present a holistic, high-level 
view of available resources. 
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Frequent tasks such as drive replacement and drive firmware updates are automated to 
reduce the burden on the administrator. 
To help understand Storage Spaces Direct, let’s begin by examining Storage Spaces in Windows 
Server 2012 R2 HA storage systems. In Windows Server 2012 R2, an HA system using Storage Spaces 
requires drive devices to be physically connected to all storage nodes. For the drive devices to be 
physically connected to all storage nodes, they need to reside in an external JBOD chassis, with each 
storage node having physical connectivity to the external JBOD. Also, because multiple storage nodes 
will be connecting to each drive, the drive devices need to be serial-attached SCSI (SAS) because the 
SAS protocol allows for this sharing where drives such as SATA do not allow multi-initiator. Because of 
these requirements, this deployment is referred to as Storage Spaces Shared JBOD to contrast it with 
Storage Spaces Direct. Figure 2-58 shows a Storage Spaces Shared JBOD deployment. 

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CHAPTER 2 | Software-defined datacenter