(S2D) Storage Space Direct, CSV

 

The storage can use Fibre Channel, iSCSI, FCoE, or SAS for shared disk storage, or use locally attached storage with Storage Spaces Direct (S2D).

Storage Spaces Direct (S2D) is a storage technology that combines multiple servers and storage media into a single cluster, essentially creating a virtual storage pool. 

S2D, or Storage Spaces Direct, is a Windows Server feature that uses a cluster of servers to create a shared storage pool. It combines the storage capacity of multiple servers into a single, virtual storage resource, allowing for easier data management and scaling. 

Instead of having a SOFS(Scale-out File Server) that is comprised of a cluster servers and a SAS network, S2D is a cluster that’s made of up servers with direct-attached storage (DAS). The supported disks include SAS HDDs and SSDs of the past, but S2D also supports:
- SATA disks: HHDs and SSDs can be very affordable
- NVMe: Non-Volatile Memory Express disks PCIe connected SSDs that offer huge amounts of IOPS, where one model I checked out offers up to 122,000 IOPS.

 

S2D is designed to use local disks on each node.These local disks are pooled together by S2D into a single virtual Storage Pool, visible to all cluster nodes. S2D handles data distribution, mirroring/parity, fault tolerance, etc., across nodes and disks.

S2D does not use traditional SAN-style LUNs. It is a hyper-converged infrastructure (HCI) technology. Each node contributes local disks (NVMe, SSDs, HDDs), which S2D aggregates into a single software-defined storage pool. From that pool, virtual disks are created — these are then formatted (usually with ReFS, though NTFS is also supported). The virtual disks are not LUNs in the traditional SAN sense, but volumes exposed to the OS or cluster.

 

 

 

LUNs are a way to identify and address individual storage devices within a storage area network (SAN)
A LUN is a unique numerical identifier assigned to a physical or virtual storage device, like a hard drive or a portion of a hard drive, within a SAN. It's how a server (client) identifies and interacts with a specific storage volume on the network. 

 

 

 

Cluster Shared Volumes (CSV) enable multiple nodes in a failover cluster to simultaneously have read-write access to the same LUN (disk) that is provisioned as an NTFS volume. (In Windows Server 2012 R2, the disk can be provisioned as NTFS or Resilient File System (ReFS).) With CSV, clustered roles can fail over quickly from one node to another node without requiring a change in drive ownership, or dismounting and remounting a volume. CSV also help simplify the management of a potentially large number of LUNs in a failover cluster.