How to display Linux related WWID details using lsscsi to manage with Linux multipathing and VxVM

Description

This article describes how to display World-Wide Identification (WWID) related information for Linux based devices.

Veritas Dynamic Multipathing (DMP) and Linux Multi-pathing (DM-Multipath) cannot co-exist without implementing specific "blacklist" & VxVM device exclusion restrictions.

Disks should be managed by only one multipathing solution. Either by Veritas Dynamic Multi-pathing (DMP) or Linux Multi-pathing (DM-Multipath).

The user may wish to manage the OS boot devices using Linux Multi-pathing, which requires adding a blacklist exception and excluding the disk from Veritas DMP.

Individual disks can be blacklisted by specifying its World-Wide Identification (WWID) . 
 

The WWID can be obtained for a single disk (/dev/sdc) by running the following command:

Example:

# /lib/udev/scsi_id --whitelisted --replace-whitespace --device=/dev/sdc
3600508b1001cbd89313f1d9cdd60dfa6

The above WWID "3600508b1001cbd89313f1d9cdd60dfa6" would then be populated in the /etc/multipath.conf file.


It is also possible to list all WWIDs for devices as follows:
 

STEPS
 

1.] A list of WWIDs can be displayed for Linux based devices using the lsscsi command:

# lsscsi -i -s
[0:2:0:0]    disk    DELL     PERC H730 Mini   4.29  /dev/sda   361866da068a36f00280c286d9db3aa5d   298GB
[0:2:1:0]    disk    DELL     PERC H730 Mini   4.29  /dev/sdb   361866da068a36f00280c294eab2018e5   298GB
[15:0:0:0]   disk    HITACHI  OPEN-V           8301  /dev/sde   360060e80124fdd0050404fdd00000022  5.36GB  <<<<
[15:0:0:1]   disk    HITACHI  OPEN-V           8301  /dev/sdf   360060e80124fdd0050404fdd00000027  5.36GB
[15:0:0:2]   disk    HITACHI  OPEN-V           8301  /dev/sdg   360060e80124fdd0050404fdd00000028  5.36GB
[15:0:0:3]   disk    HITACHI  OPEN-V           8301  /dev/sdh   360060e80124fdd0050404fdd00000029  5.36GB
[15:0:0:4]   disk    HITACHI  OPEN-V           8301  /dev/sdi   360060e80124fdd0050404fdd00000032  5.36GB
[15:0:0:5]   disk    HITACHI  OPEN-V           8301  /dev/sdj   360060e80124fdd0050404fdd00000033  5.36GB



In this instance, "sde" has the following WWID "360060e80124fdd0050404fdd00000022" 

The required WWID entry can then be manually added to the blacklist_exceptions section of the /etc/multipath.conf file.

Additional WWIDs can be added as shown in the below example.


2.] Edit the /etc/multipath.conf and add specific WWIDs for the OS configured devices under blacklist_exceptions section.


# cat /etc/multipath.conf
defaults {
        find_multipaths yes
        user_friendly_names yes
}

blacklist {
wwid ".*"
}

blacklist_exceptions {
           wwid "3600508b1001cbd89313f1d9cdd60dfa6"
           wwid "360060e80124fdd0050404fdd00000022"
}

3.]  Restart the multipathd service

# systemctl reload multipathd.service

Verify Linux multi-pathing detects the device

# multipath -ll
 

4.] The blacklisted devices must now be excluded from Veritas VxVM & DMP control using:
 

# vxdmpadm exclude dmpnodename=dmpnode_name

Exclude the DMPNODE which is now under Linux Multi-pathing control, so the two multi-pathing solutions do not conflict with each other.
 

VxVM exclusion
 

Identify the DMPNODE name for the OS device to be managed by Linux Multi-pathing and exclude it from VxVM & DMP.
 

# vxdisk -eo alldgs list | grep sde
fred_disk_0 auto:LVM       -            -           LVM                  sde            sse

The corresponding DMPNODE for the sde must be excluded from VxVM's view, by using:


# vxdmpadm exclude dmpnodename=fred_disk_0

The above "exclude" operation will populate the /etc/vx/vxvm.exclude file. This ensures the DMPNODE is consistently excluded from VxVM's view and avoids DMP probing the Linux multi-pathed device.