Automatically reconfiguring a storage memory topology

A storage cluster, comprising:

• a plurality of storage nodes;
• each of the plurality of storage nodes having a controller and at least one authority that is transferable to another one of the plurality of storage nodes, each controller coupled to each other through an interconnect;
• the controller and each such authority of each of the plurality of storage nodes configured to decide, independent of each other such authority of the plurality of storage nodes, which of a plurality of redundancy schemes to apply to distribute the user data and metadata throughout the plurality of storage nodes;
• and
• the plurality of storage nodes configured to employ erasure coding to reconfigure redundancy of the user data responsive to one of adding or removing a storage node.

A method for accessing user data in a plurality of storage nodes of a storage cluster having nonvolatile solid-state memory, comprising:

• distributing the user data throughout the plurality of storage nodes through erasure coding, wherein each of a plurality of authorities of the plurality of storage nodes is configured to, independent of each other of the plurality of storage nodes, select which of a plurality of redundancy schemes to use when a storage node distributes a portion of the user data throughout the plurality of storage nodes, and each of the plurality of authorities is transferable from one storage node to another storage node in the storage cluster;
• changing membership of the plurality of storage nodes;
• and
• reconfiguring redundancy of the user data in the plurality of storage nodes, by at least one of the plurality of authorities, responsive to the changing membership.