On Tue, Apr 21, 2009 at 10:43 PM, Konrad Rzeszutek <konrad@xxxxxxxxxxxxxxx> wrote: > On Tue, Apr 21, 2009 at 05:26:40PM +0800, 谢纲 wrote: >> Hi, >> >> I find there will be different name order of sd device when connecting >> different array. My case is as following: >> I have a SUSE server, and two array (let's say host, array1 and >> array2. Two arrays are from different vendor). They are connected >> through FC. There is two HBA controllers(let's say c1,c2) on host. >> case1: host is connected to array1. >> sd driver will generate the name orderly for each HBA controller. For examle: >> c1: /dev/sda /dev/sdb /dev/sdc >> c2:/dev/sdd /dev/sde /dev/sdf >> >> case2: host is connected to array2. >> sd driver will generate the name ramdonly for each HBA controller. For examle: >> c1: /dev/sda /dev/sdd /dev/sde >> c2:/dev/sdb /dev/sdc /dev/sdf >> >> Why is the order different with different array? > > You can also use /dev/disk/by-path instead of the /dev/sdX names. > >> >> I went through the sd probe part of linux scsi subsystem. In >> scsi_probe_lun, an inquery command will be issued to probe the lun. >> This request will be executed with scsi_execute. This function is sync >> and blocked. Because it invokes the blk_execute_rq to exec the >> request, in blk_execute_rq: >> rq->end_io_data = &wait; >> blk_execute_rq_nowait(q, bd_disk, rq, at_head, blk_end_sync_rq); >> wait_for_completion(&wait); >> >> According to above, sd driver probes one lun at one time. Before >> respone to current inquery is returned, no other inquery is issued. In >> another word, the proccess of probe lun is sync and blocked. > > Per HBA. Since you have two HBA's they can both probe the LUNs at the > same time. Or depending on how the array works, it allows you to probe > on the first HBA first, and then on the second. I noticed that the async lun scaning was added to sd driver in later version of kernel.It seems that the scan of scsi host would start only after the scan of previous finished: if (!shost->async_scan) scsi_complete_async_scans(); Is this means that for the luns which belong to the same host controller, the naming order is preserved? > >> The whole sequence of proble lun is: >> scan host controller->scan target->probe and add lun. >> So, the whole procedure of sd probe should be serial. but why is >> there case2? Is it because the different order of executing command on >> array? But according the code of sd driver, it seems it's not the >> root cause. >> >> Thanks, >> >> >> >> -- >> Xie Gang >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-scsi" in >> the body of a message to majordomo@xxxxxxxxxxxxxxx >> More majordomo info at http://vger.kernel.org/majordomo-info.html > -- Xie Gang -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
