When your dealing with SAN attached disks on Linux system, you may need to increase or release them for various reasons. In order to perform these operations, you must know which LUN is assigned to which OS Underlying disk.
Identify SAN LUN underlying OS disk is straight forward with lsscsi command on Linux. In this quick article, we will describe how to find all storage devices attached to a Linux system.
lsscsi stands for list small Computer System Interface, which uses information in sysfs to list SCSI devices (or hosts) currently attached to the Linux system.
Run the following lsscsi command to map the block device against the attached storage devices (SAN) on the Linux system.
According the below output. Device 'sda' is a virtual disk that was attached from VMWare and used for OS partition. Devices 'sdb to sdi' were mapped from the Storage array, which is why these are showing the LUN number against each block devices.
# lsscsi --scsi [0:0:0:0] disk VMWare Virtual disk 2.0 /dev/sda - [0:0:1:0] disk EMC SYMMETRIX 6544 /dev/sdb 3600d0230000000000e11404639558820 [0:0:2:0] disk EMC SYMMETRIX 6544 /dev/sdc 3600d0230000000000e11404639558821 [0:0:3:0] disk EMC SYMMETRIX 6544 /dev/sdd 3600d0230000000000e11404639558822 [0:0:4:0] disk EMC SYMMETRIX 6544 /dev/sde 3600d0230000000000e11404639558823 [1:0:0:0] disk EMC SYMMETRIX 6544 /dev/sdf 3600d0230000000000e11404639558824 [1:0:1:0] disk EMC SYMMETRIX 6544 /dev/sdg 3600d0230000000000e11404639558825 [1:0:2:0] disk EMC SYMMETRIX 6544 /dev/sdh 3600d0230000000000e11404639558826 [1:0:3:0] disk EMC SYMMETRIX 6544 /dev/sdi 3600d0230000000000e11404639558827 [3:0:0:0] cd/dvd NECVMWar VMWare IDE CDR10 1.00 /dev/sr0 -
The above output consists of seven parts and the details are below:
Details:
To include Disk/LUN size with lsscsi command, run:
# lsscsi --scsi --size [0:0:0:0] disk VMWare Virtual disk 2.0 /dev/sda - 70.2GB [0:0:1:0] disk EMC SYMMETRIX 6544 /dev/sdb 3600d0230000000000e11404639558820 5.36GB [0:0:2:0] disk EMC SYMMETRIX 6544 /dev/sdc 3600d0230000000000e11404639558821 10.7GB [0:0:3:0] disk EMC SYMMETRIX 6544 /dev/sdd 3600d0230000000000e11404639558822 10.7GB [0:0:4:0] disk EMC SYMMETRIX 6544 /dev/sde 3600d0230000000000e11404639558823 16.21GB [1:0:0:0] disk EMC SYMMETRIX 6544 /dev/sdf 3600d0230000000000e11404639558824 16.21GB [1:0:1:0] disk EMC SYMMETRIX 6544 /dev/sdg 3600d0230000000000e11404639558825 48.3GB [1:0:2:0] disk EMC SYMMETRIX 6544 /dev/sdh 3600d0230000000000e11404639558826 48.3GB [1:0:3:0] disk EMC SYMMETRIX 6544 /dev/sdi 3600d0230000000000e11404639558827 32.2GB [3:0:0:0] cd/dvd NECVMWar VMWare IDE CDR10 1.00 /dev/sr0 - 1.07GB
We can identify the associated disk name and its LUN number by listing the information from the following path '/dev/disk/by-id/'. However, this output shows you a lot of information, so it can be very difficult to understand for the first time.
# ls -ltrh /dev/disk/by-id | egrep -i '^scsi|^wwn' total 0 lrwxrwxrwx 1 root root 9 Jul 16 2023 scsi-3600d0230000000000e11404639558820 -> ../../sdb lrwxrwxrwx 1 root root 10 Jul 16 2023 wwn-0x600d0230000000000e11404639558820-part1 -> ../../sdb1 lrwxrwxrwx 1 root root 9 Jul 16 2023 scsi-3600d0230000000000e11404639558821 -> ../../sdc lrwxrwxrwx 1 root root 10 Jul 16 2023 wwn-0x600d0230000000000e11404639558821-part1 -> ../../sdc1 lrwxrwxrwx 1 root root 9 Jul 16 2023 scsi-3600d0230000000000e11404639558822 -> ../../sdd lrwxrwxrwx 1 root root 10 Jul 16 2023 wwn-0x600d0230000000000e11404639558822-part1 -> ../../sdd1 lrwxrwxrwx 1 root root 9 Jul 16 2023 scsi-3600d0230000000000e11404639558823 -> ../../sde lrwxrwxrwx 1 root root 10 Jul 16 2023 wwn-0x600d0230000000000e11404639558823-part1 -> ../../sde1 lrwxrwxrwx 1 root root 9 Jul 16 2023 scsi-3600d0230000000000e11404639558824 -> ../../sdf lrwxrwxrwx 1 root root 10 Jul 16 2023 wwn-0x600d0230000000000e11404639558824-part1 -> ../../sdf1
You can view detailed information for a SAN LUN using the smartctl command in Linux. Smartctl (Self-Monitoring, Analysis and Reporting Technology) is a command line tool that perform SMART tasks such as monitor the reliability of the hard drive, predict drive failures and perform various types of drive self-test.
# smartctl -a /dev/sdb smartctl 7.1 2020-04-05 r5049 [x86_64-linux-4.18.0-425.10.1.el8_7.x86_64] (local build) Copyright (C) 2002-19, Bruce Allen, Christian Franke, www.smartmontools.org === START OF INFORMATION SECTION === Vendor: EMC Product: SYMMETRIX Revision: 6544 Compliance: SPC-3 User Capacity: 5,368,709,120 bytes [5.00 GB] Logical block size: 512 bytes Rotation Rate: Solid State Device Logical Unit id: 0x3600d0230000000000e11404639558820 Serial Number: 36002345D00LP Device type: disk Transport protocol: Fibre channel (FCP-2) Local Time is: Mon Jul 17 22:48:21 2023 IST SMART support is: Available - device has SMART capability. SMART support is: Enabled Temperature Warning: Disabled or Not Supported === START OF READ SMART DATA SECTION === SMART Health Status: OK Current Drive Temperature: 0 C Drive Trip Temperature: 0 C Elements in grown defect list: 0 Error Counter logging not supported Device does not support Self Test logging
This article showed you how to use the lsscsi command to find all storage devices attached to a Linux system. Also, showed you how to view detailed information for a SAN LUN using the smartctl command in Linux.
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Good article