scsi-persistent-reservations · shipping · also SCSI PR, SCSI-3 PR

SCSI persistent reservations

SCSI persistent reservations control initiator access to a logical unit using registered keys and a selected reservation type.

Registration and reservation are separate operations. Write Exclusive permits only the holder to write, while Write Exclusive, Registrants Only permits all registered initiators to write. The scope is the LUN, not its partitions. Persistence through power loss depends on applicable support and configuration, including APTPL; do not infer it from the word persistent. Linux's simplified PR interface has stronger persistence and multipath expectations than the optional SPC behaviors.

Relations

related

io-fencing, scsi, multipath-io, logical-unit-number, initiator-target

Citations

1. Douglas Gilbert, sg3_utils: sg_persist(8), registration, reservation and APTPL semantics. (accessed 2026-10-11)
2. Linux kernel documentation: Block layer support for Persistent Reservations. (accessed 2026-10-11)
3. Red Hat Enterprise Linux 6, Fence Configuration Guide 4.28: SCSI Persistent Reservations (historical guide, LUN scope). (accessed 2026-10-11)
4. Storage fencing: why a lost heartbeat does not stop writes (accessed 2026-10-11)

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