Because OneFS protects its data at the file-level, any inconsistencies or data loss is isolated to the unavailable or failing device—the rest of the file system remains intact and available.
For example, an eight-node PowerScale H7000 cluster protected at +2n:1d sustains three simultaneous drive failures—one in each of three nodes. Even in this degraded state, I/O errors would only occur on the very small subset of data housed on all three of these drives. The remainder of the data striped across the other 157 drives would be unaffected. Contrast this behavior with a traditional RAID 6 system, where losing more than two drives in a RAID set renders it unusable and necessitates a full restore from backups.
Similarly, in the unlikely event that a portion of the file system does become corrupt (whether as a result of a software or firmware issue) or a media error occurs where a section of the disk has failed, only the portion of the file system associated with this area on disk would be affected. All healthy areas would still be available and protected.
Referential checksums of both data and metadata are used to catch silent data corruption (data corruption not associated with hardware failures). The checksums for file data blocks are stored as metadata outside the blocks that they reference, and thus provide referential integrity.
