Alexander Nezhinsky wrote: > Backing store based on SCSI Generic driver (sg), v.3. > allows to route scsi commands to the native scsi devices > unchanged. It uses Direct I/O (dio) to avoid memcopy > to the buffer cache. > > Using sg allows asynchronous execution, commands are > written to a sg-backed char device, completions are > read from the same device, which can be polled > asynchronously. > > This bs provides significant performance improvement when > working with native scsi devices. In a setup, where > the scsi devices are exported by a tgt with bs_null, > and both links (from initiator to target and from the > target to the "backing-store" target) are iSER/IB > sustained bandwidth of 1450 MB/s for READ and > 1350 MB/s for WRITE is achieved. This to be compared to > 700-800 MB/s when running with bs_rdwr in the same setup. > Some improvements are seen with IOPS as well: > 60 kIOPS for READ, 38 kIOPS for WRITE > (compared to 31/35KIOPS with bs_rdwr). > Hi, I applied this patch and it works, but I noticed that the serial number reported by the device (using sg_inq) returned 'beaf11' instead of the real physical serial number. Does it mean that the inquiry command is not transferred to the device and handled internally? Thanks, Doron -- To unsubscribe from this list: send the line "unsubscribe stgt" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
