A FlexCache volume is a sparsely populated volume on a local storage system that is backed by a volume on a different, possibly remote, storage system. A sparsely populated volume, sometimes called a sparse volume, provides access to data in the remote volume without requiring that all the data be in the sparse volume.
You use FlexCache volumes to speed up access to remote data, or to offload traffic from heavily accessed volumes. Because the cached data must be ejected when the data is changed, FlexCache volumes work best for data that does not change often.
When a client requests data from the FlexCache volume, the data is read from the origin system and cached on the FlexCache volume. Subsequent requests for that data are then served directly from the FlexCache volume. This improves performance when the same data is accessed repeatedly, because after the first request, the data no longer has to travel across the network, or be served from an overloaded system.