Prior to the File Level Redundancy (FLR) feature, availability and resilience of a Lustre file system relied entirely on the availability and resilience of its backend storage devices, servers, software, and network. Lustre software File Level Replication mitigates this dependency by specifying a mirroring file layout for data across multiple OSTs so that file data remains available in the event of OSS or OST failure, for whatever reason. Data integrity can be checked and repaired by comparing mirrors.
The FLR feature is split into several implementation phases in order to reduce complexity and allow functional sub-units to be available for use earlier for workloads that can use them. The various development phases and components are described in the following documents.