Topologies

Experimental SAS topologies

         server1
       2x /  \  2x (2 dual_port HBAs)
     sassw1 sassw2
         \   /
         jbod1-1

Single host, dual SAS HBA, dual SAS switch (sassw1 and sassw2) connected to single JBOD SIM (jbod1-1). It is not a tree topology anymore, not sure it is really supported. sas_discover output:

$ sas_discover
server1
|--host29 
|  `---8x--expander-29:0  
|          |---1x--end_device-29:0:0 enclosure sassw1 
|          `---4x--expander-29:1  
|                  |---1x--end_device-29:1:60 enclosure jbod1-1 
|                  |---4x--expander-29:2  
|                  |       `---1x--end_device-29:2:0 enclosure sassw2 
|                  `-- 60 block devices (use -vv for details)
`--host30 
   `---8x--expander-30:0  
           |---1x--end_device-30:0:0 enclosure sassw2 
           `---4x--expander-30:1  
                   |---1x--end_device-30:1:60 enclosure jbod1-1 
                   |---4x--expander-30:2  
                   |       `---1x--end_device-30:2:0 enclosure sassw1 
                   `-- 60 block devices (use -vv for details)

But in that case, sas_devices failed to get any device parent enclosure (all devices are orphans) because the enclosure_devices are missing from sysfs.

Warning: no enclosure set for sdao in /sys/class/sas_end_device/end_device-29:1:39/device/target29:0:40/29:0:40:0
Warning: no enclosure set for sdcw in /sys/class/sas_end_device/end_device-30:1:39/device/target30:0:40/30:0:40:0
Warning: no enclosure set for sdah in /sys/class/sas_end_device/end_device-29:1:32/device/target29:0:33/29:0:33:0

With sas_sd_snic_alias, only the bay identifier works, not the enclosure identifier:

$ sas_sd_snic_alias sdh
unknown_snic-bay6

Indeed, no enclosure_device is found in /sys/block/sdh