When you are working in a storage environment, it is often desirable to add, remove or re-size storage devices. Once storage is allocated we need to scan and verify the allocated storage SAN disk.
In this guide, I will show commands to check/identify the attached LUN information in a Linux system.
What is a LUN
A LUN is a Logical Unit Number. It can be used to refer to an entire physical disk, or a subset of a larger physical disk or disk volume. The physical disk or disk volume could be an entire single disk drive, a partition (subset) of a single disk drive, or disk volume from a RAID controller comprising multiple disk drives aggregated together for larger capacity and redundancy.
1. Check attached LUN or SAN disk in Linux
To check the attached LUN from a storage device in Linux, we can use the /proc/scsi/scsi file content but it will give you some information and you can not be able to distinguish physical attached drive to LUN. Display the content as below as below
# cat /proc/scsi/scsi
Attached devices:
Host: scsi0 Channel: 00 Id: 00 Lun: 00
Vendor: VMware, Model: VMware Virtual S Rev: 1.0
Type: Direct-Access ANSI SCSI revision: 02
Host: scsi0 Channel: 00 Id: 01 Lun: 00
Vendor: VMware, Model: VMware Virtual S Rev: 1.0
Type: Direct-Access ANSI SCSI revision: 02
Host: scsi0 Channel: 00 Id: 02 Lun: 00
Vendor: VMware, Model: VMware Virtual S Rev: 1.0
Type: Direct-Access ANSI SCSI revision: 02
Host: scsi2 Channel: 00 Id: 00 Lun: 00
Vendor: NECVMWar Model: VMware IDE CDR10 Rev: 1.00
Type: CD-ROM ANSI SCSI revision: 05
Host: scsi3 Channel: 00 Id: 00 Lun: 00
Vendor: LIO-ORG Model: block Rev: 4.0
Type: Direct-Access ANSI SCSI revision: 05
Host: scsi3 Channel: 00 Id: 00 Lun: 01
Vendor: LIO-ORG Model: block2 Rev: 4.0
Type: Direct-Access ANSI SCSI revision: 05
Host: scsi3 Channel: 00 Id: 00 Lun: 02
Vendor: LIO-ORG Model: rhelblock Rev: 4.0
Type: Direct-Access ANSI SCSI revision: 05Normally Luns would be showing as Host: scsi3 Channel: 00 Id: 00 Lun: 00
Below is another example of the same file where it's using a different storage vendor.
# cat /proc/scsi/scsiAttached devices:
Host: scsi0 Channel: 00 Id: 00 Lun: 00
Vendor: HP 36.4G Model: MAN3367MC Rev: HP05
Type: Direct-Access ANSI SCSI revision: 02
Host: scsi2 Channel: 00 Id: 00 Lun: 00
Vendor: COMPAQ Model: HSV110 (C)COMPAQ Rev: 2003
Type: Unknown ANSI SCSI revision: 02
Host: scsi2 Channel: 00 Id: 00 Lun: 02
Vendor: COMPAQ Model: HSV110 (C)COMPAQ Rev: 2003
Type: Direct-Access ANSI SCSI revision: 02
Host: scsi2 Channel: 00 Id: 00 Lun: 03
Vendor: COMPAQ Model: HSV110 (C)COMPAQ Rev: 2003
Type: Direct-Access ANSI SCSI revision: 02
Host: scsi2 Channel: 00 Id: 01 Lun: 00
Vendor: COMPAQ Model: HSV110 (C)COMPAQ Rev: 2003
Type: Unknown ANSI SCSI revision: 02
Host: scsi2 Channel: 00 Id: 01 Lun: 02
Vendor: COMPAQ Model: HSV110 (C)COMPAQ Rev: 2003
Type: Direct-Access ANSI SCSI revision: 02
Host: scsi2 Channel: 00 Id: 01 Lun: 03
Vendor: COMPAQ Model: HSV110 (C)COMPAQ Rev: 2003You can use iscsiadm (only used when storage using iscsi target) command to get information about attached lun.
# iscsiadm -m session -P 3
iSCSI Transport Class version 2.0-870
version 6.2.0.873-35
Target: iqn.2017-06.com.linoxide:target1 (non-flash)
Current Portal: 172.16.20.139:3260,1
Persistent Portal: 172.16.20.139:3260,1
**********
Interface:
**********
............
............
************************
Attached SCSI devices:
************************
Host Number: 3 State: running
scsi3 Channel 00 Id 0 Lun: 0
Attached scsi disk sdd State: running
scsi3 Channel 00 Id 0 Lun: 1
Attached scsi disk sde State: running
scsi3 Channel 00 Id 0 Lun: 2
Attached scsi disk sdf State: runningYou can also check below path for lun information.
# ls /dev/disk/by-path/
ip-172.16.20.139:3260-iscsi-iqn.2017-06.com.linoxide:target1-lun-0
ip-172.16.20.139:3260-iscsi-iqn.2017-06.com.linoxide:target1-lun-1
ip-172.16.20.139:3260-iscsi-iqn.2017-06.com.linoxide:target1-lun-2
pci-0000:00:07.1-ata-2.0
pci-0000:00:10.0-scsi-0:0:0:0
pci-0000:00:10.0-scsi-0:0:0:0-part1
pci-0000:00:10.0-scsi-0:0:0:0-part2
pci-0000:00:10.0-scsi-0:0:1:0
pci-0000:00:10.0-scsi-0:0:2:0Also, try using dmesg command
# dmesg | grep -i "attached "
Attached scsi disk sda at scsi0, channel 0, id 0, lun 0
Attached scsi disk sdb at scsi2, channel 0, id 0, lun 2
Attached scsi disk sdc at scsi2, channel 0, id 0, lun 3
Attached scsi disk sdd at scsi2, channel 0, id 1, lun 22. Using multipath command
Redhat default multipathing service is multipathd daemon. Below commands are from a server that has a multipathing enabled using multipathd daemon and from its output you can check OS identified Lun information.
# multipath -v4 -ll
Jun 21 04:58:40 | loading /lib64/multipath/libcheckdirectio.so checker
Jun 21 04:58:40 | loading /lib64/multipath/libprioconst.so prioritizer
Jun 21 04:58:40 | Discover device /sys/devices/pci0000:00/0000:00:07.1/ata2/host2/target2:0:0/2:0:0:0/block/sr0
Jun 21 04:58:40 | sr0: device node name blacklisted
Jun 21 04:58:40 | Discover device /sys/devices/pci0000:00/0000:00:10.0/host0/target0:0:0/0:0:0:0/block/sda
................................
................................
===== paths list =====
uuid hcil dev dev_t pri dm_st chk_st vend/prod/rev dev_st
0:0:0:0 sda 8:0 -1 undef ready VMware, ,VMware Virtual S running
0:0:1:0 sdb 8:16 -1 undef ready VMware, ,VMware Virtual S running
0:0:2:0 sdc 8:32 -1 undef ready VMware, ,VMware Virtual S running
3:0:0:0 sdd 8:48 -1 undef ready LIO-ORG ,block running
3:0:0:1 sde 8:64 -1 undef ready LIO-ORG ,block2 running
3:0:0:2 sdf 8:80 -1 undef ready LIO-ORG ,rhelblock running
Jun 21 04:58:40 | directio checker refcount 6
Jun 21 04:58:40 | directio checker refcount 5
Jun 21 04:58:40 | directio checker refcount 4
Jun 21 04:58:40 | directio checker refcount 3
Jun 21 04:58:40 | directio checker refcount 2
Jun 21 04:58:40 | directio checker refcount 1
Jun 21 04:58:40 | unloading const prioritizer
Jun 21 04:58:40 | unloading directio checkerConclusion
Hope this guide helped you to gather lun information on your Linux operating system. Please provide your comments and suggestion in the below section.
About The Author
Bobbin Zachariah
Bobbin Zachariah is an experienced Linux engineer who has been supporting infrastructure for many companies. He specializes in Shell scripting, AWS Cloud, JavaScript, and Nodejs. He has qualified Master’s degree in computer science. He holds Red Hat Certified Engineer (RHCE) certification and RedHat Enable Sysadmin.
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