On Thu, Nov 14, 2024 at 10:51:09AM +1100, Dave Chinner wrote: > Specifically to this "stream hint" discussion: go look at the XFS > filestreams allocator. Those are rally two different things - file streams is about how to locate data into a single hardware write streams. SCSI/NVMe streams including streams 2.0 (FDP) that this thread is about is about telling the hardware about these streams, and also about allowing the file systems (or other user of the storage) to pack into the actual underlying hardware boundaries that matter for deleting/overwriting this data. Funnily enough Hans and I were just recently brainstorming on how to tie both together for the zoned xfs work. > SGI wrote an entirely new allocator for XFS whose only purpose in > life is to automatically separate individual streams of user data > into physically separate regions of LBA space. One of the interesting quirks of streams/FDP is that they they operate on (semi-)physical data placement that is completely decoupled from LBA space. So if a file system or application really wants to track LBA vs physical allocations separately it gives them a way to do that. I don't really know what the advantage of having to track both is, but people smarted than me might have good uses for it.
