A cloud storage infrastructure is the hardware and software framework that supports the computing requirements of a private or public cloud storage service. Both public and private cloud storage infrastructures are known for their elasticity, scalability and flexibility.
Public clouds have massive multi-tenancy infrastructures and all customers share the same hardware and supporting software. Additional storage resources can be purchased on-demand for unexpected workloads and dropped when workloads decrease. Private cloud infrastructures use the same server, storage and virtualization technologies as public cloud storage providers, but the hardware and software components are owned and managed in-house. Private storage clouds are usually for a single tenant, although larger enterprises may use multi-tenancy features to segregate access by departments or office locations.
Some organizations may want the control that private cloud infrastructures offer, but don't want to deal with housing, running and maintaining an in-house cloud storage infrastructure. If this is the case, they can contract with a cloud storage service provider for equipment to support cloud operations. In this provisioning model, which is known as Infrastructure-as-a-Service (IaaS), the service provider owns the equipment (storage, hardware, servers and networking components) and the client typically is charged on a per-use basis.
Unlike traditional local storage, which is block-based, cloud storage infrastructures are usually object-based. Access to object-based storage is made possible through a Web services application programming interface (API) using the Simple Object Access Protocol (SOAP) or Representational State Transfer (REST) protocol. The infrastructure is often built with commodity hardware and servers are clustered so that the storage capacity of each can be aggregated into a single pool. In this infrastructure configuration, capacity expansion is made possible by adding another server to the cluster.