Compatibility with Oracle Cloud Infrastructure

A principal objective of Private Cloud Appliance is to allow you to consume the core Oracle Cloud Infrastructure services from the safety of your own on-premises network, behind your own firewall. The infrastructure services provide a foundation for building PaaS and SaaS solutions; the deployed workloads can be migrated between the public and the private cloud infrastructure with minimal or no modification required. For this purpose, Private Cloud Appliance offers API compatibility with Oracle Cloud Infrastructure.

As a rack-scale system, Private Cloud Appliance can be considered the smallest deployable unit of Oracle Cloud Infrastructure, aligned with the physical hierarchy of the public cloud design:

Hierarchy Concept	Oracle Cloud Infrastructure Design	Oracle Private Cloud Appliance Mapping
Realm	A Realm is a superset of Regions, and the highest physical subdivision of the Oracle cloud. There are no cross-realm features. Oracle Cloud Infrastructure currently consists of a Realm for Commercial Regions and a Realm for Government Cloud Regions.	The concept of a Realm exists in Private Cloud Appliance, but it has no practical function. It allows the appliance to participate in any Realm.
Region	A Region is a geographic area. An Oracle Cloud Infrastructure Region is composed of at least three Availability Domains. It is possible to migrate or replicate data and resources between Regions.	Private Cloud Appliance is designed as a single Region. Because this private region is disconnected from any other systems, it has no practical function. Domain and system identifiers are used in system configuration instead, and mapped to the region and realm values.
Availability Domain	An Availability Domain consists of one or more data centers. Availability Domains are isolated from each other; they have independent power and cooling infrastructure and separate internal networking. A failure in one Availability Domain is highly unlikely to impact others. Availability Domains within the same region are interconnected through an encrypted network with high bandwidth and low latency. This is a critical factor in providing high availability and disaster recovery.	Each Private Cloud Appliance is configured as an Availability Domain. Multiple installations are distinct from each other: they do not function as Availability Domains within the same region.
Fault Domain	A Fault Domain is a grouping of infrastructure components within an Availability Domain. The goal is to isolate downtime events due to failures or maintenance, and make sure that resources in other Fault Domains are not affected. Each Availability Domain contains three Fault Domains. Fault Domains provide anti-affinity: the ability to distribute instances so that they do not run on the same physical hardware.	Private Cloud Appliance adheres to the public cloud design: each Availability Domain contains three Fault Domains. A Fault Domain corresponds with one or more physical compute nodes.

Private Cloud Appliance also aligns with the logical partitioning of Oracle Cloud Infrastructure. It supports multiple tenancies, which are securely isolated from each other by means of tunneling and encapsulation in the appliance underlay network. Tenancies are hosted on the same physical hardware, but users and resources that belong to a given tenancy cannot interact with other tenancies. In addition, the Compute Enclave – which refers to all tenancies collectively, and to the cloud resources created and managed within them – is logically isolated from the Service Enclave, from where the appliance infrastructure is controlled. Refer to Enclaves and Interfaces for more information.

The Compute Enclave interfaces provide access in the same way as Oracle Cloud Infrastructure. Its CLI is identical while the browser UI offers practically the same user experience. API support is also identical, but limited to the subset of cloud services that Private Cloud Appliance offers.

The consistency of the supported APIs is a crucial factor in the compatibility between the public and private cloud platforms. It ensures that the core cloud services support resources and configurations in the same way. More specifically, Private Cloud Appliance supports the same logical constructs for networking and storage, manages user identity and access in the same way, and offers the same compute shapes and images for instance deployment as Oracle Cloud Infrastructure. As a result, workloads set up in a private cloud environment are easily portable to Private Cloud Appliance and vice versa. However, due to the disconnected operating mode of the private cloud environment, workloads must be migrated offline.