Although VMware’s new virtual SAN (VSAN) service stole the storage show at VMworld 2013, it’s not the first product of its kind on the market (Nutanix and SimpliVity are light years ahead), nor is it the first in this overall class of storage service from VMware. Prior to VSAN, VMware made available their vSphere Storage Appliance software, but compared to VSAN, VSA is hardly in the same league.
Whereas VSAN is designed to scale to up to 32 nodes in a cluster (although it only supports eight right now), VSAN is designed to support no more than three nodes, making it a perfect fit for vSphere’s Essentials SKU. In addition VSA doesn’t support the use of solid state disks in a mature way. VSAN actually requires that user have SSD in their cluster and it uses it as a read cache. VSA also scales to only 16 TB, but VSAN can scale up to much greater capacities.
In addition, VSA is a storage appliance with a potential single point of failure. VSAN is a service that’s built right into the vSphere kernel as an essential service and is ultimately intended to support enterprise-class storage needs.
In short, VSA is intended to be for only the smallest of environments or for secondary storage. There are also other virtual storage appliances on the market from companies such as HP. However, in the long run, even for small environments, VSAN may be a better option, particularly where performance is required.