User guide

7.4 LINUX SCSI DEVICE ENUMERATION

Linux enumerates SCSI devices in order of Host:BUS:ID:LUN

# lsscsi -g

[0:0:0:0] disk SEAGATE ST373207LC D703 /dev/sda /dev/sg0

[0:0:6:0] process PE/PV 1x2 SCSI BP 1.0 - /dev/sg1

[1:0:0:0] disk DDN S2A 6620 1.03 /dev/sdd /dev/sg3

[1:0:0:1] disk DDN S2A 6620 1.03 /dev/sde /dev/sg5

[1:0:0:2] disk DDN S2A 6620 1.03 /dev/sdg /dev/sg7

[2:0:0:0] disk DDN S2A 6620 1.03 /dev/sdb /dev/sg2

[2:0:0:1] disk DDN S2A 6620 1.03 /dev/sdc /dev/sg4

[2:0:0:2] disk DDN S2A 6620 1.03 /dev/sdf /dev/sg6

The lsscsi utility is part of some Linux distributions, but is also available for free download. It

displays SCSI path information, Vendor and Product inquiry strings, block devices, and

associated SCSI generic devices in a nice easy to read output.

7.5 FUNCTIONING MULTIPATH OUTPUT (ON RHEL 5 AND SLES 10)

# multipath -ll

mpath19 (360001ff0721160000000002688e10002) dm-2 DDN,S2A 6620

[size=21T][features=1 queue_if_no_path][hwhandler=0][rw]

\_ round-robin 0 [prio=50][active]

\_ 1:0:0:2 sdg 8:96 [active][ready]

\_ round-robin 0 [prio=10][enabled]

\_ 2:0:0:2 sdf 8:80 [active][ready]

mpath19 (360001ff0721160000000002688e10002) dm-2 DDN,S2A 6620

^ ^ ^ ^ ^

| | | |_______ Vendor

| | |__________ Sysfs Name

| |_____________________________ WWID of the Device

|_________________________________________________ User Defined Alias Name

Product and Vendor are returned from the SCSI inquiry string

The sysfs name is the device mapper SCSI block device name

WWID is the unique identifier for the multipath device, which includes OEM vendor

strings, owning controller MAC, and LUN id’s

The alias name is optional and can be defined in /etc/multipath.conf in conjunction with

enabling user_friendly_names