About erasure coding topologies

An erasure coding topology consists of a set of HCP systems and active/active replication links that connect those systems. Within an erasure coding topology, each system must have at least two paths to each other system. Each path can consist of any number of systems and links, but the paths cannot have any systems or links in common.

When you create an erasure coding topology, you select the systems to include in it. The systems you select must be part of an existing active/active replication ring topology or fully connected active/active replication topology.

For each pair of selected systems that are connected to each other in the underlying replication topology, if the pair has only one active/active replication link between them, that link is automatically included in the erasure coding topology. If any pair of the selected systems is connected by more than one active/active link, you select which one of those links to include in the erasure coding topology.

An erasure coding topology does not automatically include the tenants on the links in the underlying replication topology. Instead, you select the tenants to include in an erasure coding topology from all the replication-enabled tenants defined on the systems in the topology. Each tenant you select is automatically added to each link in the erasure coding topology.

When you create an erasure coding topology, it's in the active state. If you want to stop using the active topology for erasure-coded protection, you need to retire the topology.

Retiring an erasure coding topology causes the Geo-distributed Erasure Coding service to restore object chunks to full-copies or, on systems where the objects are on metadata-only storage tiers, delete the chunks. While the chunks are being restored or deleted, the topology is in the retiring state.

When all the systems in a retiring erasure coding topology have no more chunks that are the result of that topology, the state of the topology changes to retired. Once a topology is retired, you can delete it. Deleting an erasure coding topology does not cause any systems, links, tenants, namespaces, or objects to be deleted.

A system can be in at most five erasure coding topologies concurrently. Only one of those topologies can be active. The rest must be either retiring or retired.