Hello, I'm using a 2.4.18-ac3 kernel and the multipath module in order to ensure automatic IO path failover. The systems connect to a FC SAN environment. New logical disks are added/removed from the SAN periodically. Unfortunatelly, linux's raid subsystem uses major and minor numbers in the superblock in order to identify members for all raid types - including multipath. This causes the multipath module to fail when attempting to identify the members. When the scsi driver is loaded, the bus is scanned and all the available devices/targets/luns are added to the scsi subsystem and are allocated a major and minor number. Say initially, the following are available scsi1, bus0, target0, lun0 scsi1, bus0, target0, lun1 scsi1, bus0, target0, lun2 scsi2, bus0, target0, lun0 scsi2, bus0, target0, lun1 scsi2, bus0, target0, lun2 They will be mapped as /dev/sda /dev/sdb /dev/sdc /dev/sdd /dev/sde /dev/sdf and 8,0 8,16 8,32 8,48 8,64 8,80 majors,minors respectivelly. The disks with LUNs 0, 1, 2 are the same but are viewed on two paths: /dev/sda - /dev/sdd /dev/sdb - /dev/sde /dev/sdc - /dev/sdf Multipath is created in this configuration and works properly. Now LUN1 is removed. The new configuration is: scsi1, bus0, target0, lun0 scsi1, bus0, target0, lun2 scsi2, bus0, target0, lun0 scsi2, bus0, target0, lun2 Unfortunatelly, majors and minors became 8,0 8,16 8,32 8,48 So scsi1, bus0, target0, lun2 is now 8,16 instead of 8,32 However, the raid superblock still has 8,32 in it - this confuses multipath - I even managed to get it crashing really ugly at some point. The problem is partially caused by md identifying devices based on major,minor and partially caused by the fact the the scsi subsystem has no way (afaik) of mapping device,channel,target,lun to major,minor pairs. This mapping is being performed dynamically by devfs for user-space programs, but kernel modules that need to access devices via major,minor have this problem. Is there something I am missing? Is this a lack in the kernel? Thanks, Ionut - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
