(S2D) 헷갈리는 개념들 (SAN, NAS, S2D, LUN, shared volumem, Cluster Shared Volume)

🔹 Key Storage Terms:

1. SAN (Storage Area Network)

• Type: Architecture
• What: A high-speed network that connects servers to block-level storage (often via Fibre Channel or iSCSI).
• Key concept: Storage is external to the servers.
• Common in: Enterprise environments before hyperconverged systems.
• Example component: LUNs.

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2. NAS (Network Attached Storage)

• Type: Architecture
• What: A storage system that provides file-level storage over a network (e.g., via SMB, NFS).
• Key concept: Clients access files, not blocks.
• Common in: File sharing, backups, media servers.

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3. LUN (Logical Unit Number)

• Type: Block storage concept (within SAN)
• What: A virtualized portion of a physical disk presented to a host as a disk.
• Used in: SAN setups, not in S2D.
• Not applicable in: S2D or NAS directly.

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4. S2D (Storage Spaces Direct)

• Type: Microsoft’s software-defined, hyper-converged storage
• What: Aggregates local disks from multiple servers into one storage pool; creates virtual disks from that pool.
• Key concept: No SAN; all storage is local and pooled.

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5. Shared Volume

• Type: General term
• What: A volume accessible by multiple nodes/clients.
• Example: SMB share on NAS, LUN in SAN, or CSV in S2D.

Term	Layer	Nodes
SAN	Architecture	External block storage fabric
NAS	Architecture	File storage over network
LUN	Storage Unit	Block storage unit in SAN
S2D	Architecture	Pools local disks; no SAN needed
Shared Volume	Concept	Generic term for shared access
Cluster Shared Volume (CSV)	Windows Failover Cluster Feature	Shared ReFS/NTFS volume for cluster nodes

 

🔸What is the difference between S2D and CSV?

Feature	Storage Spaces Direct (S2D)	Cluster Shared Volumes (CSV)
Type	Storage architecture	Cluster volume feature
What it does	Pools local disks across nodes into one storage pool and creates virtual disks	Allows multiple cluster nodes to access the same volume
Purpose	To provide hyperconverged, software-defined storage	To provide shared access to volumes in a Windows Failover Cluster
Uses CSVs?	✅ Yes	CSV is a component used by S2D
Storage layer	Below CSVs — it provides the actual storage	Above storage — it’s how that storage is shared in the cluster
Works without CSV?	❌ No — S2D depends on CSV to share volumes across the cluster	✅ Yes — CSV can be used in clusters with SANs too

 

🔸 SAN LUN format

Storage Type	Format as NTFS?	Format as ReFS?	Use as CSV?
Local Disk	✅	✅	✅ (if clustered)
SAN LUN	✅	✅	✅
S2D Virtual Disk	✅	✅ (preferred)	✅
NAS Share (e.g. SMB/NFS)	❌	❌	❌ (not block storage)

 

✅ Correct Ways to Provide Shared Storage to a Failover Cluster:

1. SAN (Fibre Channel or iSCSI) with LUNs
2. Storage Spaces Direct (S2D) using local disks
3. Azure Shared Disks (in cloud scenarios)
4. Storage Replica + DFS (in some cases, not for CSVs)