Tier III is the Uptime Institute topology classification for concurrently maintainable sites, which have redundant capacity components and multiple independent distribution paths, though only one path is active at a time. Any component or path can be removed for planned maintenance without shutting down the IT load, but the site is not necessarily fault tolerant against an unplanned failure.
Category: Resilience & Availability · Subcategory: Tier & Class Systems · Part of the AIDC Technical Terminology reference.