Description

A World Wide Name (WWN) is a unique identifier assigned by the IEEE (Institute of Electrical and Electronics Engineers) for network storage devices.

A WWN is a number that is hard-coded into network storage devices, such as fiber channels (FC) and advanced technology attachments (ATA). In simple terms, a WWN is like a MAC address, but for network storage devices.

A WWN is primarily implemented in SANs with multiple attached storage devices, which helps system administrators (SA) uniquely categorize and identify storage components.
 

Veritas DMP is capable of exposing WWN related content for discovered controllers.

# vxdmpadm getctlr all
LNAME             PNAME                                    VENDOR               CTLR-ID
=====================================================================================================
c13               c13                                      QLogic Corporation   20:00:00:24:ff:1a:77:72
c11               c11                                      QLogic Corporation   20:00:00:24:ff:1a:77:74
c15               c15                                      QLogic Corporation   20:00:00:24:ff:1a:77:73
c14               c14                                      -                    -
c0                c0                                       -                    -

Depending on environmental factors, Veritas may not be able to expose WWN details following a reboot.
 

Whilst it is essential the OS (Operating System) is able to see the WWN information for Veritas DMP to display it, changes may be required to work with RedHat.
 

Sample RedHat commands:

List the controller (HBA) ids:

# find /sys/class/fc_host/*/ -name 'node_name'
/sys/class/fc_host/host11/node_name
/sys/class/fc_host/host13/node_name
/sys/class/fc_host/host14/node_name
/sys/class/fc_host/host15/node_name

List the controller WWN details:

# find /sys/class/fc_host/*/ -name 'node_name' |xargs cat
0x20000024ff1a7774
0x20000024ff1a7775
0x20000024ff1a7772
0x20000024ff1a7773

# find /sys/class/fc_host/*/ -name 'port_name' |xargs cat
0x21000024ff1a7774
0x21000024ff1a7775
0x21000024ff1a7772
0x21000024ff1a7773

List the controller port state:

# find /sys/class/fc_host/*/ -name 'port_state' |xargs cat
Online
Online
Online
Online

vxpath_links script

The /lib/udev/vxpath_links script is processed during the boot process and parses the device names to create the /dev/vx/.dmp/devname symlinks pointing to /dev/disk/by-path/physname.

The /etc/vx/vxpath_links script is used to generate WWN & PWWN information whenever devices are discovered in the /dev/vx/.dmp directory.

Whenever vxesd (eventsource) starts, it reads the /dev/vx/.dmp contents and populates the WWN & PWWN information in /etc/vx/ddlconfig.info file.

VxVM tracks the hardware physical path by referencing the "/dev/vx/.dmp/" directory contents, which contains symbolic links between sd names and hardware paths.

DMP reads the /dev/vx/.dmp/devname symlink to get the physical path name for saving the path-specific configuration changes.

Modify

The /etc/vx/vxpath_links and /lib/udev/vxpath_links script needs to include the following section highlighted in BOLD below within the gather_ddlconfig function:

gather_ddlconfig()
{
               dev=$1
               wwnpath=$2
               fcdevice=0
               srpdevice=0

               DEV=`readlink --canonicalize /sys/block/$dev/device`
               tgt_path="${DEV%/*}"
               hba_path="${tgt_path%/host[0-9]*}"
               ctlr_id=`echo $tgt_path | sed 's/.*host\([0-9]*\).*/\1/'`

               # Populate ctlr physical info
               if [ ! -f "$DMP_BYPATH_LINK/c$ctlr_id" ]; then

                              ctlr_physname=`echo $wwnpath | \
                        sed 's/\(\-[a-z]*\-\).*//' 2>/dev/null`
                ln -sf $ctlr_physname $DMP_BYPATH_LINK/c$ctlr_id
               fi

               is_fc_device=`echo $wwnpath | grep -c "\-fc\-"`
               if [ $is_fc_device -ne 0 ]; then
                              fcdevice=1
               elif [ -d $tgt_path/../$SRP_HOST_DIR ]; then
                              srpdevice=1
               else
                              return;
               fi

Veritas builds the WWN and PWWN details as follows:
 

1.    VxVM calls “vxpath_links ALL” to build the paths under /dev/vx/.dmp/HBA

2.    vxesd generates /etc/vx/ddlconfig.info by scanning all the /dev/vx/.dmp/ &  /dev/vx/.dmp/HBA directory contents

On a server where the PWWN details are reported

#  ls -la /dev/vx/.dmp/HBA
total 0
drwxr-x--- 6 root root  120 Feb 23 15:27 .
drwxr-x--- 3 root root 7580 Apr 14 11:05 ..
drwxr-x--- 6 root root  140 Apr 14 10:55 2
drwxr-x--- 6 root root  140 Apr 14 11:00 3
drwxr-x--- 6 root root  140 Apr 14 11:05 4
drwxr-x--- 6 root root  140 Apr 14 11:05 5

On a server where the PWWN details are NOT reported:

#  ls -la /dev/vx/.dmp/HBA
total 0
drwxr-x--- 2 root root  40 Apr  9 14:50 .
drwxr-x--- 3 root root 720 Apr 14 10:01 ..

3.    The Device Discover Layer (DDL) builds the ddl_entity_list  from /etc/vx/ddlconfig.info file, which includes the port id information

4.    vxdmpadm gets the PWWN from property list plist by req_ddl_get_port_info through vold, the plist is populated from ddl_entity_list

The Veritas script can be run as follows  “#sh -x /etc/vx/vxpath_links ALL” which generates the /dev/vx/.dmp/HBA file contents

Veritas DMP on H/W path of the sd device under /dev/disk/by-path to discover some device attributes, such as PWWN.