HCP System Management Help


About replication

Replication, an HCP service, is the process of keeping selected tenants and namespaces in two HCP systems in sync with each other. This entails copying object creations, object deletions, metadata changes, and other information between the two systems. Typically, the two systems are in separate geographic locations and are connected by a high-speed wide area network.

A replication topology is a configuration of HCP systems wherein each system is related to each other system through a path of one or more replication relationships. The HCP system from which you’re viewing the replication topology is called the local system. Any other system in the replication topology is called a remote system.

Replication has several purposes:

If the local system becomes unavailable (for example, due to network issues), a remote system can provide continued data availability.

If the local system suffers irreparable damage, a remote system can serve as a source for disaster recovery.

If multiple HCP systems are widely separated geographically, each system may be able to provide faster data access for some applications than the other systems can, depending on where the applications are running.

If an enterprise has several satellite offices, an HCP system at a central facility can consolidate data from the HCP systems at those outlying locations.

If the content verification or protection service discovers objects it cannot repair on the local system, the service can use object data and metadata from a remote system to make the needed repairs. For more information on these services, see Administering HCP.

If an object cannot be read from the local system (for example, because a node is unavailable), HCP can try to read it from a remote system. HCP tries to do this only if:

oThe namespace that contains the object is involved in replication.

oThe namespace has the read-from-remote-system feature enabled.

oThe object has already been replicated. Users can check object metadata to determine whether an object has been replicated.

oThe replication networks for the local and remote systems can both use the same IP mode (IPv4 or IPv6).

For more information on the read-from-remote-system feature, see Managing a Tenant and Its Namespaces or Managing the Default Tenant and Namespace.

If the local system is unavailable, HTTP requests to that system can be automatically serviced by a remote system without the client needing to modify the target URL. The remote system can service a request only if:

oThe namespace named in the URL is replicated to the remote system

oThe namespace named in the URL is configured to accept requests redirected from other HCP systems

oThe HCP systems involved use a shared DNS for system addressing

oThe replication networks for the two systems can both use the same IP mode (IPv4 or IPv6)

Additionally, unless you’re using a load balancer that can target the requests to the remote system:

oThe DNS must be configured to support redirection between the two systems

oThe HCP system that’s unavailable must have been configured to allow DNS failover to other systems

For more information on the service-by-remote-system feature, see Managing a Tenant and Its Namespaces or Managing the Default Tenant and Namespace.

For information on:

Replication networks, see Selecting the network for replication

Configuring HCP in the DNS, see Administering HCP

Configuring HCP to support DNS failover, see Managing DNS failover

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