Primary storage in the cloud comes in similar forms to traditional primary storage (NAS or Block) A majority of the products we have examined leverage a hybrid model where there is a small investment in local storage that is then replicated to a cloud provider. Changes to the data is snapshotted and replicated in either real time or near real time to the cloud provider of your choice. The advantage cloud enabled primary storage has is that it is very easy to test. You can test a 10TB configuration without installing 10TB of storage.”]
Source: https://www.darkreading.com/database-security/primary-storage-in-the-cloud-ready-for-prime-time