Explanation
Volume storage is allocated and mounted as a virtual hard drive within IaaS implementations, and it can be maintained and used the same way a traditional file system can. Object storage uses a flat structure on remote services that is accessed via opaque descriptors, structured storage resembles database storage, and unstructured storage is used to hold auxiliary files in conjunction with applications hosted within a PaaS implementation.

When a key management system is outside of the cloud environment hosting the application, availability is a primary concern because any access issues with the encryption keys will render the entire application unusable.