SYSTEM Cited by 1 source

Meta Power Loss Siren (PLS)

Power Loss Siren (PLS) is Meta's system for persisting in-memory data when server racks have lost power, using battery backup to provide a persistence window during power-loss events.

PLS was originally disclosed in Meta's December 2021 blog post as a rack-level capability for graceful data persistence under power failure.

Role in Instantaneous PowerLoss Storm

PLS is one of the foundational capabilities that makes region-scale power-loss validation possible — it ensures storage and compute nodes can flush critical in-memory state to persistent media during the brief battery-backed window after power loss.

Seen in

• sources/2026-06-03-meta-lights-out-systems-on-validating-instant-power-loss-readiness — named as a foundational power-loss-tolerance capability