On Mon, Mar 20, 2023 at 10:22:41AM -0700, Bart Van Assche wrote: > How to achieve optimal performance with REQ_OP_ZONE_APPEND for SCSI > devices? My understanding of how REQ_OP_ZONE_APPEND works for SCSI devices > is as follows: > * ATA devices cannot support this operation directly because there are > not enough bits in the ATA sense data to report where appended data > has been written. ATA doesn't really have autosense in the SCSI way. It could be handled the same way that CDL completions are handled. That is a complete mess, and between CDL and Zone Append we'll probably eventually need an extended FIS for SATA if we want to keep ATA alive. > * T10 has not yet started with standardizing a zone append operation. Time to get it started then! > * The code that emulates REQ_OP_ZONE_APPEND for SCSI devices (in > sd_zbc.c) serializes REQ_OP_ZONE_APPEND operations (QD=1). Because that's the only thing that actually works. > * To achieve optimal performance, QD > 1 is required. If you have something magic that works, this code is the place to take advantage of it.
