In the past few months it’s become clear to me that people are confusing Storage Spaces and Scale-Out File Server (SOFS). They seem to incorrectly think that one requires the other or that the terms are interchangeable. I want to make this clear:
Storage Spaces and Scale-Out File Server are completely different features and do not require each other.
The concept of Storage Spaces is simple: you take a JBOD (a bunch of disks with no RAID) and unify them into a single block of management called a Storage Pool. From this pool you create Virtual Disks. Each Virtual Disk can be simple (no fault tolerance), mirrored (2-way or 3-way), or parity (like RAID 5 in concept). The type of Virtual Disk fault tolerance dictates how the slabs (chunks) of each Virtual Disk are spread across the physical disks included in the pool. This is similar to how LUNs are created and protected in a SAN. And yes, a Virtual Disk can be spread across 2, 3+ JBODs.
Note: In WS2012 you only get JBOD tray fault tolerance via 3 JBOD trays.
Storage Spaces can be used as the shared storage of a cluster (note that I did not limit this to a SOFS cluster). For example, 2 or more (check JBOD vendor) servers are connected to a JBOD tray via SAS cables (2 per server with MPIO) instead of connecting the servers to a SAN. Storage Spaces is managed via the Failover Cluster Manager console. Now you have the shared storage requirement of a cluster, such as a Hyper-V cluster or a cluster running the SOFS role.
Yes, the servers in the cluster can be your Hyper-V hosts in a small environment. No, there is no SMB 3.0 or file shares in that configuration. Stop over thinking things – all you need to do is provide shared storage and convert it into CSV that is used as normal by Hyper-V. It is really that simple.
Yes, JBOD + Storage Spaces can be used in a SOFS as the shared storage. In that case, the virtual disks are active on each cluster node, and converted into CSVs. Shares are created on the CSVs, and application servers access the shares via SMB 3.0.
Scale-Out File Server (SOFS)
The SOFS is actually an active/active role that runs on a cluster. The cluster has shared storage between the cluster nodes. Disks are provisioned on the shared storage, made available to each cluster node, added to the cluster, and converted into CSVs. Shares are then created on the CSV and are made active/active on each cluster node via the active/active SOFS cluster role.
SOFS is for application servers only. For example Hyper-V can store the VM files (config, VHD/X, etc) on the SMB 3.0 file shares. SOFS is not for end user shares; instead use virtual file servers that are stored on the SOFS.
Nowhere in this description of a SOFS have I mentioned Storage Spaces. The storage requirement of a SOFS is cluster supported storage. That includes:
- SAS SAN
- iSCSI SAN
- Fibre Channel SAN
- FCoE SAN
- PCI RAID (like the Dell VRTX)
- … and SAS attached shared JBOD + Storage Spaces
Note that I only mentioned Storage Spaces with the JBOD option. Each of the other storage options for a cluster uses hardware RAID and therefore Storage Spaces is unsupported.
Storage Spaces works with a JBOD to provide a hardware RAID alternative. Storage Spaces on a shared JBOD can be used as cluster storage. This could be a small Hyper-V cluster or it could be a cluster running the active/active SOFS role.
A SOFS is an alternative way of presenting active/active storage to application servers. It requires cluster supported storage, which can be a shared JBOD + Storage Spaces.