On Mon, 24 Jun 2019, Martin K. Petersen wrote: > > Perhaps they do not set stripe_width using io_opt? I did a grep to see > > if any of them did, but I didn't see them. How is stripe_width > > indicated by RAID controllers? > > The values are reported in the Block Limits VPD page for each SCSI block > device and are thus set by the SCSI disk driver. IOW, the RAID > controller device drivers have nothing to do with this. > > For RAID controllers specifically, the controller firmware will fill out > the VPD fields for each virtual SCSI disk when you configure a RAID > set. For pretty much everything else, the Block Limits come straight > from the device itself. > > Also note that these values aren't specific to RAID controllers at > all. Most new SCSI devices, including disk drives and SSDs, will fill > out the Block Limits VPD page one way or the other. Even some USB > storage devices are providing this page. Thanks, that makes sense. Interesting about USB. > > If they do set io_opt, then at least my Areca 1883 does not set io_opt > > as of 4.19.x. I also have a LSI MegaRAID 3108 which does not report > > io_opt as of 4.1.x, but that is an older kernel so maybe support has > > been added since then. > > I have several MegaRAIDs that all report it. But it depends on the > controller firmware. > > > Is it visible through sysfs or debugfs so I can check my hardware > > support without hacking debugging the kernel? > > To print the block device topology: > > # lsblk -t > > or look up io_opt in sysfs: > > # grep . /sys/block/sdX/queue/optimal_io_size > > You can also query a SCSI device's Block Limits directly: > > # sg_vpd -p bl /dev/sdX Perfect, thank you for that. I've tried the following controllers that I have access to. One worked (hspa/HP Gen8 Smart Array Controller), but the others I tried are not providing VPDs: * LSI 2108 (Supermicro) * LSI 3108 (Dell) * Areca 1882 * Areca 1883 * Fibrechannel 8gbe connected to a Storwize 3700 ~]# sg_vpd -p bl /dev/sdb VPD page=0xb0 fetching VPD page failed > If you want to tinker, you can simulate a SCSI disk with your choice of > io_opt: > > # modprobe scsi_debug opt_blks=N > > where N is the number of logical blocks to report as being the optimal > I/O size. Neat, thanks for the hint! -Eric > > -- > Martin K. Petersen Oracle Linux Engineering >
