A virtual storage area network (virtual SAN, VSAN or vSAN) is a logical representation of a physical storage area network (SAN). A VSAN abstracts the storage-related operations from the physical storage layer, and provides shared storage access to the applications and virtual machines by combining the servers' local storage over a network into a single or multiple storage pools.

The use of VSANs allows the isolation of traffic within specific portions of the network. If a problem occurs in one VSAN, that problem can be handled with a minimum of disruption to the rest of the network. VSANs can also be configured separately and independently.

Technology

Operation

A VSAN operates as a dedicated piece of software responsible for storage access, and depending on the vendor, can run either as a virtual storage appliance (VSA), a storage controller that runs inside an isolated virtual machine (VM)[1] or as an ordinary user-mode application, such as StarWind Virtual SAN, or DataCore SANsymphony. Alternatively it can be implemented as a kernel-mode loadable module, such as VMware vSAN, or Microsoft Storage Spaces Direct (S2D).[2] A VSAN can be tied to a specific hypervisor, known as hypervisor-dedicated, or it can allow different hypervisors, known as hypervisor-agnostic.[3]

Different vendors have different requirements for the minimum number of nodes that participate in a resilient VSAN cluster. The minimum requirement is to have at least 2 for high availability.[4]

All-flash versus hybrid VSAN

Data center operators can deploy VSANs in an all-flash environment or a hybrid configuration, where flash is only used at the caching layer, and traditional spinning disk storage is used everywhere else. All-flash VSANs are higher performing, but as of 2019 were more expensive than hybrid networks.[5]

Protocols

For sharing storage over a network, VSAN utilizes protocols including Fibre Channel (FC), Internet Small Computer Systems Interface (iSCSI), Server Message Block (SMB), and Network File System (NFS), as well as proprietary protocols.

Applications

A VSAN fills a similar role as physical SAN infrastructure, but is also used for workload virtualization which can include databases, virtual desktop infrastructure (VDI) environments, file servers, CRM systems, and other enterprise applications.[6]

VSANs can be used for remote branch office networks, using low-cost commodity hardware.[4]

There are also applications with DMZ, an isolated network that sits outside a company's firewall, and areas with space constraints, such as vessels, where a reduced hardware footprint 2-3 node deployment has a better chance of fitting.

By being able to work on top of commodity hardware, a VSAN is often used for building highly available networks across two or more sites that are combined in a single cluster, a type of deployment known as stretched clustering.

A VSAN can also create highly available hybrid cloud environments by combining existing on-premises resources with public cloud environments.[7]

Advantages

The primary advantage of a VSAN is its ability to provide shared storage. It also increases the resiliency of storage systems by allowing the creation of redundant data copies across the servers in a VSAN cluster. It does this while requiring less hardware and power consumption than a physical SAN. Using a VSAN for local storage provides other resiliency options including mirroring or erasure coding with different parity levels.[6]

Another advantage is that unlike a typical fabric that is resized switch-by-switch, a VSAN can be resized port-by-port.

Similar concepts

A VSAN is often associated with hyperconvergence, a concept which refers to unifying computing, networking, and storage resources, within a single server. Similarly, a VSAN shifts away from having a separate physical storage layer and required networking stack, and instead combines storage from multiple nodes into a virtualized and consolidated storage layer. VSANs take control of the storage-related operations, access and features allowing the implementation of data deduplication, data compression, high availability and other features, on commodity x86 server hardware. VSAN is also associated with software-defined storage (SDS).[8] However, VSAN can be also used in converged architectures where VSAN is deployed on dedicated storage nodes as a cluster, and presents the shared storage over a network to compute nodes.

See also

References

  1. ↑ "Virtual storage appliance (VSA)". Techtarget. November 1, 2012. Retrieved July 8, 2021.
  2. ↑ "Competitors and Alternatives to SANsymphony". Gartner. Retrieved July 8, 2021.
  3. ↑ "VDI hypervisor selection: Does it matter what you pick?". TechTarget. June 15, 2012. Retrieved July 29, 2021.
  4. 1 2 "Deploy a 2-node StarWind VSAN Free for VMware ESXi 6.5". Tech Coffee. April 18, 2017. Retrieved July 9, 2021.
  5. ↑ "VMware vSAN: What Is It, and How Does It Help Businesses?". BizTech Magazine. December 23, 2019. Retrieved August 3, 2021.
  6. 1 2 "VMware vSAN vs. SAN: What are the differences?". TechTarget. September 10, 2020. Retrieved July 29, 2021.
  7. ↑ "What is hybrid cloud? Everything you need to know". Tech Target. May 1, 2021. Retrieved July 9, 2021.
  8. ↑ "What Is Software Defined Storage? Features & Benefits". Enterprise Storage Forum. February 22, 2018. Retrieved July 8, 2021.
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