Hybrid cloud storage is an approach to managing storage that uses both local and off-site resources.
Ideally, a hybrid cloud implementation behaves as if it is homogeneous storage except there are policy engines in place to keep frequently used data on-site while simultaneously moving inactive data to the cloud in a transparent manner.
Combining internal and public cloud storage into a single heterogeneous storage cloud without custom integration is only possible if the internal and external storage clouds run the same cloud storage software. Hybrid cloud storage is most often implemented through an application program interface (API) that allows an in-house or commercial application to tap into a public cloud with representational state transfer (REST) or by using a cloud storage appliance provided by the cloud storage vendor.
See also: cloud computing, private cloud, hybrid cloud