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What guidelines, if any, are there for determining if VMware Virtual SAN is right for our environment?
The first thing you need to know about VMware's Virtual SAN (vSAN) feature is that it's not a true SAN. A hardware-based SAN allows you to provision storage and then use that storage however you want. A VMware vSAN, on the other hand, can only be used for storing virtual machines. If you have physical servers in your environment, those servers can't connect to a virtual SAN and use it for storage as they would be able to with a traditional SAN.
A VMware vSAN is just a VMware cluster in which the various cluster nodes provide storage capacity. Each cluster node must contain at least one SATA or SAS disk (aside from the one the hypervisor is installed on) and one enterprise-grade solid-state drive (SSD). The vSAN software pools the available hard disk drives from across the clustered hosts and makes them available as vSAN storage.
Although at least one SSD is required in each clustered host, the SSD isn't used to provide capacity. Instead, it's used for caching purposes as a way to speed up read and write I/O.
VMware's vSAN software is based around the use of direct-attached storage. If you've already invested heavily in a physical SAN environment and typically use 1U servers with very limited internal storage, VMware vSAN might not be the best choice for your environment. On the other hand, organizations that lack the budget, expertise or desire to deploy a physical SAN could benefit from a vSAN because it provides SAN-like functionality without requiring dedicated hardware.
It's also worth noting that VMware envisions scenarios in which vSANs could coexist with physical SANs. Until then, the best thing you can do is to compare its limitations to your company's limitations and try to determine whether it can satisfy a business need you can't otherwise meet.
VMware vSAN 6.6 includes encryption and analytics