FUA

FUA is an acronym that most commonly refers to Force Unit Access in the context of data storage and computer I/O. Force Unit Access denotes a flag or option in some write commands that instructs the storage device to commit data to non-volatile media, bypassing or bypassing enough caching to ensure durability at the time the command completes.

In practical terms, a write with FUA requires the device to perform the actual write to the physical medium before reporting success. This reduces the risk of data loss in events such as power failures or crashes, which is important for databases, transaction systems, and journaling file systems. The trade-off is typically reduced write performance, since data may be written more slowly than when it is permitted to use cache.

Semantics and availability of FUA vary by protocol and device. It is commonly seen in SCSI as a write operation with the FUA attribute, and in some ATA/SATA contexts as a comparable instruction to bypass cache. Not all storage controllers or drives honor FUA, and some may implement equivalent durability guarantees through other mechanisms such as write-through caching or explicit flush commands.

Other, less common uses of the acronym FUA exist in different fields, but in technology writing and data management, Force Unit Access remains the primary referent. For more durable storage behavior, users should consult device documentation to confirm support and correct usage of FUA.