I have addressed the question in several of the Virtual SAN presentations I have delivered, but I realized that this was an ongoing topic of discussion and one which we needed to provide more details in order to satisfy everyone that has been wondering about this topic. I figured it was time to put together some form of OFFICIAL collateral providing in-depth details around this topic.
So, like any storage system, VMware Virtual SAN makes use of data locality. Virtual SAN uses a combination of algorithms that take advantage of both temporal and spatial locality of reference to populate the flash-based read caches across a cluster and provide high performance from available flash resources.
For more details on this topic, download the new Understanding Data Locality in VMware Virtual SAN white paper from the link below:
For future updates on Virtual SAN (VSAN), Virtual Volumes (VVols), and other Software-defined Storage technologies as well as vSphere + OpenStack be sure to follow me on Twitter: @PunchingClouds