Microsoft Storage Spaces Direct is a feature in Windows Server 2016 that pools server storage to build a highly available and scalable software-defined storage systems for Hyper-V virtual machines.
Storage Spaces Direct makes two copies of data to other nodes in the cluster. Each node runs as a fault domain and data is spread across the fault domains to prevent data loss if a disk fails. If a disk fails, data will be replicated to another disk in the cluster so three copies of data are present at all times.
By adding more nodes to the cluster, Storage Spaces Direct will automatically pool the storage into the cluster. Up to 240 disks and 12 nodes can be added to a cluster.
Storage Spaces Direct uses Server Message Block (SMB) 3.0 for communication between storage nodes.
Storage Spaces Direct can be deployed two ways. In the hyper-converged deployment, the Hyper-V clusters and storage are on the same hardware; Microsoft says this model is more appropriate for smaller scale-out arrangements. In the private cloud storage deployment, the Hyper-V clusters and storage resources are separate; Microsoft recommends this model for larger scale-out deployments.
By separating the Hyper-V clusters and storage in the private cloud deployment, administrators can scale and manage the storage and compute resources independently.
The hyper-converged model allows the resources to be scaled and managed together. This deployment can be used as the primary storage of a Hyper-V VM file or as the secondary storage for Hyper-V Replica VM files.
Using Storage Spaces Direct requires: either a NIC capable of remote direct memory access or a pair of NIC ports; a cluster with at least four nodes running Windows Server 2016; each node is a member of an Active Directory.