Determining a devices WWID in Linux

For multipath drivers connecting to storage area networks (SAN), it is useful in your /etc/multipath.conf to blacklist devices. This prevents the multipath driver from attempting to use the device(s).

To find out a drive’s WWID, run the following command:

>scsi_id -g -u -s /block/sda

This will return a WWID. On my system it was returned as 36001e4f034bf55000f98fe8606dc88df.

Now you can put this in the blacklist section of /etc/multipath.conf as:

blacklist {
devnode “^(ram|raw|loop|fd|md|dm-|sr|scd|st)[0-9]*”
devnode “^hd[a-z]”
devnode “^sda”
devnode “^sda[0-9]”
devnode “^sdb”
devnode “^sdb[0-9]”
wwid    “36001e4f034bf55000f98fe8606dc88df”
device {
vendor DELL
product “PERC|Universal|Virtual”
}
}

This will now prevent the multipath driver from attempting to manage /dev/sdc.