How to Find SAN disk LUN id in Linux

In some cases, you may need to find a block device mapped against a logical unit number (LUNs) for filesystem (FS) expansion or disaster recovery (DR) activity.

Also, this information is required if you want to work with the storage team to troubleshoot or fix a high latency or disk error on a specific block device.

Refer the following article to map ASM disks against storage LUNs.

This information can be found at the following location. However, you will not find mapping details for multipath LUNs because it shows the name of the multipath device instead of the block devices.

ls -ltrh /dev/disk/by-id

Therefore, since there is no direct command to find this information in Linux, this can be achieved by writing a small shell script, which we will discuss further in this article.

In this article, we will show you how Disks mapped to SAN LUNs in Linux.

Shell Script to check SAN disk LUN id in Linux

This shell script helps you to identify which SAN disk LUN id is assigned to which OS Underlying disk on Linux.

In this shell script we are using the lsblk command and smartctl command to achieve the results.

vi block_device_mapping_with_LUN.sh

#!/bin/bash
echo "Device_Name" "|" "LUN_ID"
echo "---------------------"
for lunmap in `lsblk | grep disk | grep ^s | awk '{print $1}'`
do echo -e "$lunmap \t--> $(smartctl -a /dev/$lunmap | grep "Logical Unit id" | awk -F":" '{print $2}')"
done

Set an executable permission to ‘block_device_mapping_with_LUN.sh’ file.

chmod +x block_device_mapping_with_LUN.sh

Finally run the script to view the results.

sh block_device_mapping_with_LUN.sh

Device_Name | LUN_ID
---------------------
sda --> 
sdb --> 3600d0230000000000e1140463955737c
sdc --> 3600d0230000000000e114046395577cd
sdd --> 3600d0230000000000e11404639558cc5

If you want to run the script on a single line instead of the steps above, use the below one. This one liner script will map Linux system disks against storage LUNs as shown below.

echo "Device_Name" "|" "LUN_ID"; echo "---------------------"; for lunmap in `lsblk | grep disk | grep ^s | awk '{print $1}'`; do echo -e "$lunmap \t--> $(smartctl -a /dev/$lunmap | grep "Logical Unit id" | awk -F":" '{print $2}')"; done

Device_Name | LUN_ID
---------------------
sda --> 
sdb --> 3600d0230000000000e1140463955737c
sdc --> 3600d0230000000000e114046395577cd
sdd --> 3600d0230000000000e11404639558cc5

Checking SAN disk LUN mapping using lsscsi command in Linux

lsscsi stands for list small Computer System Interface. The lsscsi command lists information about SCSI/Sata devices attached to the system.

The command below will display a list of LUNs attached to the system, their block devices mapping and size.

lsscsi --scsi --size

[0:0:0:0]   disk   VMWare   Virtual disk   2.0    /dev/sda   - 60.3GB
[0:0:2:0]   disk   EMC      SYMMETRIX      6544   /dev/sdb   3600d0230000000000e1140463955737c  16.1GB
[0:0:3:0]   disk   EMC      SYMMETRIX      6544   /dev/sdc   3600d0230000000000e114046395577cd  16.1GB
[0:0:4:0]   disk   EMC      SYMMETRIX      6544   /dev/sdd   3600d0230000000000e11404639558cc5  16.1GB

Wrapping Up

In this tutorial, we’ve shown you to identify/check/match LUN presented from SAN with underlying OS disk on Linux.

If you have any questions or feedback, feel free to comment below.