VMware vSAN (formerly Virtual SAN)

VMware vSAN (formerly Virtual SAN) is a hyper-converged, software-defined storage (SDS) product developed by VMware that pools together direct-attached storage devices across a VMware vSphere cluster to create a distributed, shared data store. The user defines the storage requirements, such as performance and availability, for virtual machines (VMs) on a VMware vSAN cluster and vSAN ensures that these policies are administered and maintained.

vSAN is part of the VMware ESXi kernel and runs on industry-standard x86 servers from original equipment manufacturers (OEMs), including Cisco, Dell EMC, Hewlett Packard Enterprise, Fujitsu, Lenovo and Supermicro. Because vSAN is a native component, it does not require additional software, and the user can enable it with a few clicks.

The distributed architecture of VMware vSAN enables the parameters of the storage policy to be enforced despite changes in virtual machine (VM) workload demands or hardware or network failures. The vSphere Web Client handles cluster administration and storage policy implementation. 

vSAN supports both hybrid and all-flash configurations using a two-tier architecture. Both configurations use a caching tier and a capacity tier. The caching tier is composed of at least one flash device per host. The capacity tier is composed of at least one flash device (for all-flash) or one magnetic disk (for hybrid) per host. vSAN combines the host's storage resources into a single, high-performance, shared data store that all the hosts in the cluster can use.

Important features

VMware vSAN includes a number of key features, although the feature set varies depending on the license type. Some of vSAN's key features are Storage Policy-Based Management, stretched clusters, checksum and software-defined data-at-rest encryption which does not require self-encrypting drive (SEDs).

vSAN 6.6 claims to deliver 50% more IOPS than previous versions of vSAN because of the way it minimizes storage latency through the use of server-side flash devices. It also includes a new health check feature that enables the administrator to see at a glance whether or not the vSAN cluster is healthy and, if it detects a problem, help diagnose the issue.

A vSAN cluster can include between 2 and 64 nodes. The vSAN 6.6 Enterprise license offers stretched clusters with local site protection, and native data-at-rest encryption designed to achieve higher availability and security with minimal CPU overhead. Both Advanced and Enterprise licenses support deduplication, compression and erasure coding data services for all-flash configurations. Erasure coding can be configured with either single or double parity protection against disk failures.

All the vSAN licenses also offer support for storage quality of service (QoS), which enables an administrator to place limits on the number of IOPS that specific VMs can consume.

Comparison of vSAN editions (Standard, Advanced, Enterprise)

VMware has different licensing options for vSAN. The three primary options are Standard, Advanced and Enterprise. There are also three licensing options intended for remote office/branch office (ROBO) environments known as ROBO Standard, ROBO Advanced and ROBO Enterprise and an additional three licensing options intended for virtual desktop infrastructure (VDI) environments known as vSAN for Desktop Standard, Advanced and Enterprise.

Each of these licensing options provides standard features such as vSphere Replication and all-flash support. On top of the standard feature set, the Advanced and ROBO Advanced licenses add support for deduplication and compression, and RAID 5 and RAID 6 erasure coding for all-flash environments.

The Enterprise edition has all the capabilities of the Advanced product, but also adds support for stretched clusters with local site protection and native data-at-rest encryption. 

Partners and competitors

VMware markets vSAN as part of its hyper-converged infrastructure offering, which also includes vSphere and vCenter.  Several hardware vendors, including Fujitsu and Lenovo, sell integrated appliances that come preinstalled with vSAN and offer full support for the integrated appliance. Dell Technologies also sells hyper-converged infrastructure appliances, including VxRail, that include VMware vSAN software. Other hardware vendors simply work with VMware to certify their x86 servers called vSAN ReadyNodes.

The main competitors for hyper-converged infrastructure appliances are Nutanix and HPE SimpliVity. Virtual SANs may also be created with software-defined storage (SDS) software products such as Microsoft Storage Spaces Direct or Red Hat Ceph Storage.

This was last updated in December 2017

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