What link costs are

Link costs let you prioritize which data center site provides a requested service when two or more data center sites exist. You can adjust link costs to reflect latency between sites.

Link costs are used by the legacy CLB service on Gateway Nodes to direct client connections, are used to prioritize which object copy is used to fulfill object retrievals, and are used by the Grid Management API and the Tenant Management API to determine which internal StorageGRID services to use.

The diagram shows a three site grid that has link costs configured between sites:
Conceptual diagram for link costs between data centers
Link costs are arbitrary relative numbers with no specific unit of measure. For example, a link cost of 50 is used less preferentially than a link cost of 25. The table shows commonly used link costs.
Link Link cost Notes
Between physical data center sites 25 (default) Data centers connected by a WAN link.
Between logical data center sites at the same physical location 0 Logical data centers in the same physical building or campus connected by a LAN.