The post mentions few ways to exactly identify/match the LUN presented from SAN with underlying OS disk.
Method 1
Execute command below command to obtain Vendor, Model and Port, Channel, SCSI-ID, LUN
# cat /proc/scsi/scsi Host: scsi2 Channel: 00 Id: 00 Lun: 29 Vendor: EMC Model: SYMMETRIX Rev: 5874 Type: Direct-Access ANSI SCSI revision: 05 Host: scsi3 Channel: 00 Id: 00 Lun: 29 Vendor: EMC Model: SYMMETRIX Rev: 5874 Type: Direct-Access ANSI SCSI revision: 05
Then execute below command:
# ls -ld /sys/block/sd*/device lrwxrwxrwx 1 root root 0 Oct 4 12:12 /sys/block/sdaz/device -> ../../devices/pci0000:20/0000:20:02.0/0000:27:00.0/host2/rport-2:0-0/target2:0:0/2:0:0:29 lrwxrwxrwx 1 root root 0 Oct 4 12:12 /sys/block/sdbi/device -> ../../devices/pci0000:20/0000:20:02.2/0000:24:00.0/host3/rport-3:0-0/target3:0:0/3:0:0:29
Now compare hostX info with target with previous command( /proc/scsi/scsi ) to obtain details which disk is mapped to which LUN ID. The numbers marked at the end represent host, channel, target and LUN respectively. so the first device in command “ls -ld /sys/block/sd*/device” corresponds to the first device scene in the command “cat /proc/scsi/scsi” command above. i.e. Host: scsi2 Channel: 00 Id: 00 Lun: 29 corresponds to 2:0:0:29. Check the highlighted portion in both commands to correlate.
To get WWID of LUN you can use the /dev/disk/by-id/ file:
# ls -la /dev/disk/by-id/ scsi-3600508b400105e210000900000490000 -> ../../dm-1 Now its easier to understand that dm-1 has WWID 3600508b400105e210000900000490000
Method 2
Another way is to use sg_map command. Make sure you have sg3-utils installed before running this command.
# yum install sg3-utils
# sg_scan -i /dev/sg2: scsi1 channel=0 id=0 lun=1 [em] type=0 SanDisk ImageMate CF-SM 0100 [wide=0 sync=0 cmdq=0 sftre=0 pq=0x0]
Above command will give mapping for devices. after this execute:
# sg_map -x /dev/sg2 0 0 2 0 0 /dev/sdc
From the outputs of 2 commands above we can determine that sg2 ( SAN DISK ) is actually /dev/sdc device
Method 3
If multipath is being used ( device-mapper ) below command can be used:
# multipath -v4 -ll mpathc (360000970000195900437533030382310) dm-1 EMC,SYMMETRIX size=253G features='1 queue_if_no_path' hwhandler='0' wp=rw `-+- policy='round-robin 0' prio=1 status=active |- 3:0:0:1 sde 8:64 active ready running `- 5:0:0:1 sdc 8:32 active ready running
How to understand the output
mpathc - user defined name 360000970000195900437533030382310 - WWID dm-1 - sys-fs name EMC - Vendor 2:0:0:29 - host,channel,scsi-id,lun
This output can be compared with the one we get with “cat /proc/scsi/scsi” command.
# cat /proc/scsi/scsi Host: scsi2 Channel: 00 Id: 00 Lun: 29 Vendor: EMC Model: SYMMETRIX Rev: 5874 Type: Direct-Access ANSI SCSI revision: 05