I found a bug/problem in the SAS_address naming in the iSCSI driver - I have a SuperMicro X9DT3-F board that has the dual 4-port controller. The Linux kernel I am using is Linux version 2.6.32-220.el6.x86_64 - problem is, the SAS_address in sysfs on both hosts collide with each other:

[adibble@mrs4010 ~]$ for i in /sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/0000:02:08.0/0000:03:00.0/host[67]/port-*/end_device-*/sas_device/end_device-*/sas_address; do echo -n "$i: "; cat $i; done

/sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/0000:02:08.0/0000:03:00.0/host6/port-6:0/end_device-6:0/sas_device/end_device-6:0/sas_address: 0x5fcfffff00000001

/sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/0000:02:08.0/0000:03:00.0/host6/port-6:1/end_device-6:1/sas_device/end_device-6:1/sas_address: 0x5fcfffff00000002

/sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/0000:02:08.0/0000:03:00.0/host6/port-6:2/end_device-6:2/sas_device/end_device-6:2/sas_address: 0x5fcfffff00000003

/sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/0000:02:08.0/0000:03:00.0/host6/port-6:3/end_device-6:3/sas_device/end_device-6:3/sas_address: 0x5fcfffff00000004

/sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/0000:02:08.0/0000:03:00.0/host7/port-7:0/end_device-7:0/sas_device/end_device-7:0/sas_address: 0x5fcfffff00000002

/sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/0000:02:08.0/0000:03:00.0/host7/port-7:1/end_device-7:1/sas_device/end_device-7:1/sas_address: 0x5fcfffff00000003

See, I have two different disks that have SAS_address 0x5fcfffff00000002 (7:0 and 6:1) so this breaks the udev /dev/disk/by-path stuff because it finds 2 disks that have identical information according to udev - so only one of them is represented by a symlink at any given time.

I think the right answer is to encode the SAS host id (the 7: part) into the SAS_address but I'm not too familiar with what SAS_address actually represents and what the correct policy on this is. Do you know or have any info?