hesela.devSCSI Disable Page Out
SCSI Disable Page Out requests low cache-retention priority for the blocks accessed by a command.
DPO=1 selects the lowest retention priority; DPO=0 uses the caching mode page. It is separate from FUA and does not establish persistence or a physical-media read. [1]
Linux v6.16 target code advertises DPO alongside FUA while treating DPO as a no-op hint. Its command parser checks support for DPO but sets SCF_FUA only for the separate FUA bit. Command acceptance therefore does not demonstrate cache eviction. [2] [3]
Relations
- related
- Force Unit Access, SCSI VERIFY, Cache admission
Limitations
- A supported retention hint does not guarantee a performance improvement or an empty cache. [2]
Citations
- Seagate SCSI Commands Reference Manual Rev. L (2020), section 3.18, p. 150: DPO and READ FUA.
- Linux v6.16 target_core_spc.c: spc_emulate_modesense and the DPO no-op implementation.
- Linux v6.16 target_core_sbc.c: sbc_check_dpofua validates DPO separately from setting SCF_FUA.
Sources & caveats
- Manual and pinned implementation review; no physical-device experiment or cache-performance measurement.