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====== Multipathing disks on SAN ======

This can be configure with Redhat or Suse distribution

https://access.redhat.com/solutions/3072701   

https://access.redhat.com/solutions/3790681  

https://access.redhat.com/solutions/41476

===== Packages installation =====

Packages installation:
  sysfsutils
  device-mapper
  device-mapper-multipath

The package « multipath-tools » content the following components:
  * multipath
/sbin/multipath: command to scan multipathing devices on the system, it creates logical definitions and update device-mapper kernel.
  * multipathd
/usr/bin/multipathd: daemon to manage and monitor multipathing devices. Logging events into syslog.
  * devmap-name
/sbin/devmap_name: allow to rename devices into kernel (use udev)
  * kpartx
/sbin/kpartx: command for mapping devmaps with device partitions.


===== 1° method to configure =====

==== Modify configuration file ====

Copy the example configuration file multipath.conf into /etc :
<cli prompt='#'>
# cp /usr/share/doc/device-mapper-multipath-0.4.7/multipath.conf.defaults /etc/multipath.conf
</cli>

Modify the file /etc/multipath.conf:
  * black lister les disques systèmes, non multipathés (fdisk –l : liste les disques)
  * décommenter le paragraphe correspondant à la baie de stockage désirée

<cli prompt='#'>
[root@BKPSRV1 etc]# cat /etc/multipath.conf
# This is a basic configuration file with some examples, for device mapper
# multipath.
# For a complete list of the default configuration values, see
# /usr/share/doc/device-mapper-multipath-0.4.7/multipath.conf.defaults
# For a list of configuration options with descriptions, see
# /usr/share/doc/device-mapper-multipath-0.4.7/multipath.conf.annotated


# Blacklist all devices by default. Remove this to enable multipathing
# on the default devices.
blacklist {
#        devnode "*"
devnode "^cciss!c[0-9]d[0-9]*"
}

## By default, devices with vendor = "IBM" and product = "S/390.*" are
## blacklisted. To enable mulitpathing on these devies, uncomment the
## following lines.
#blacklist_exceptions {
#       device {
#               vendor  "IBM"
#               product "S/390.*"
#       }
#}

## Use user friendly names, instead of using WWIDs as names.
defaults {
        user_friendly_names yes
}

devices {
device {
vendor "NETAPP "
product "LUN"
path_grouping_policy group_by_prio
getuid_callout "/sbin/scsi_id -g -u -s /block/%n"
prio_callout"/opt/netapp/santools/mpath_prio_ontap /dev/n"
features "1 queue_if_no_path"
path_checker readsector0
failback immediate
}
}
</cli>

Step #3 : Activation du mutlipathing

Il faut activer le multipathing au boot avec les commandes suivantes :
<cli prompt='#'>
# chkconfig --add multipathd
# chkconfig multipathd on
</cli>
Or 
<cli prompt='#'>
# mpathconf --enable
</cli>

Le démarrage immédiat du daemon s’effectue comme suit:
<cli prompt='#'>
# modprobe multipath 
# modprobe dm-multipath
# modprobe dm-round-robin
# /etc/init.d/multipathd start
</cli>

Step #4 : Vérifications

Vérifications :
<cli prompt='#'>
# lsmod|grep multipath
multipath              10961  0
</cli>
<cli prompt='#'> 
# lsmod|grep dm
dm_round_robin          4929  1
dm_multipath           21841  2 dm_round_robin
dm_snapshot            19073  0
dm_zero                 3649  0
dm_mirror              32465  0
dm_mod                 68097  16 dm_multipath,dm_snapshot,dm_zero,dm_mirror
 
# ps -ef|grep multipath
root      3069     1  0 15:00 ?        00:00:00 /sbin/multipathd
</cli>

Check multipath config:
<cli prompt='#'>
# /sbin/mpathconf 
multipath is disabled
find_multipaths is disabled
user_friendly_names is enabled
dm_multipath module is loaded
multipathd is chkconfiged off
</cli>

Enable with user_friendly_names and find_multipaths
<cli prompt='#'>
# /sbin/mpathconf --enable --find_multipaths y --user_friendly_names y --with_chkconfig y --with_multipathd y
</cli>

<cli prompt='#'>
[root@BKPSRV1 etc]# multipath -ll
mpath1 (360a9800050334942614a4f6377436a51) dm-10 NETAPP,LUN
[size=145G][features=1 queue_if_no_path][hwhandler=0]
\_ round-robin 0 [prio=8][active]
 \_ 0:0:0:1 sdb 8:16  [active][ready]
 \_ 1:0:0:1 sdf 8:80  [active][ready]
\_ round-robin 0 [prio=2][enabled]
 \_ 0:0:1:1 sdd 8:48  [active][ready]
 \_ 1:0:1:1 sdh 8:112 [active][ready]
mpath0 (360a98000503349424b5a4f6376687347) dm-9 NETAPP,LUN
[size=1.0T][features=1 queue_if_no_path][hwhandler=0]
\_ round-robin 0 [prio=8][active]
 \_ 0:0:1:0 sdc 8:32  [active][ready]
 \_ 1:0:1:0 sdg 8:96  [active][ready]
\_ round-robin 0 [prio=2][enabled]
 \_ 0:0:0:0 sda 8:0   [active][ready]
 \_ 1:0:0:0 sde 8:64  [active][ready]

# dmsetup ls --target=multipath
mpath7  (253, 3)
mpath6  (253, 2)
 
# dmsetup table
mpath7: 0 35692800 multipath 0 0 1 1 round-robin 0 2 1 8:16 100 8:48 100
mpath6: 0 5760 multipath 0 0 1 1 round-robin 0 2 1 8:0 100 8:32 100
VolGroup00-LogVol01: 0 4063232 linear 104:2 66650496
VolGroup00-LogVol00: 0 66650112 linear 104:2 384
</cli>

Important:
Un disque multipathé est visible dans /dev plusieurs fois:
/dev/dm-N, /dev/mapper/mpathN et /dev/mpath/mpathN
Il faut toujours créé une partition ou un volume group sur /dev/mapper/mpathN, qui est le seul device persistent.

To suppress a multipath disk or all:
  dmsetup remove <mpathxx>
  dmsetup remove_all
  
<cli prompt='#'> 
# systemctl reload multipathd
</cli>


===== 2° method to configure =====

==== Using command line ====

For redhat or fedora
<cli prompt='#'>
[root@BKPSRV1 etc]# /sbin/mpathconf --find_multipaths y
[root@BKPSRV1 etc]# multipath -v3
Nov 17 11:39:18 | loading /lib64/multipath/libcheckdirectio.so checker
Nov 17 11:39:18 | loading /lib64/multipath/libprioconst.so prioritizer
Nov 17 11:39:18 | sda: not found in pathvec
Nov 17 11:39:18 | sda: mask = 0x3f
Nov 17 11:39:18 | sda: dev_t = 8:0
Nov 17 11:39:18 | sda: size = 104857600
Nov 17 11:39:18 | sda: vendor = AIX     
Nov 17 11:39:18 | sda: product = VDASD           
Nov 17 11:39:18 | sda: rev = 0001
Nov 17 11:39:18 | sda: h:b:t:l = 0:0:1:0
Nov 17 11:39:18 | sda: path state = running

Nov 17 11:39:18 | sda: 51200 cyl, 64 heads, 32 sectors/track, start at 0
Nov 17 11:39:18 | sda: serial = 000e583a0000d40000000143bb7850cf.17
Nov 17 11:39:18 | sda: get_state
Nov 17 11:39:18 | sda: path checker = directio (controller setting)
Nov 17 11:39:18 | sda: checker timeout = 120000 ms (sysfs setting)
Nov 17 11:39:18 | directio: starting new request
Nov 17 11:39:18 | directio: io finished 4096/0
Nov 17 11:39:18 | sda: state = up
Nov 17 11:39:18 | sda: uid_attribute = ID_SERIAL (internal default)
Nov 17 11:39:18 | sda: uid = SAIX_VDASD_000e583a0000d40000000143bb7850cf.17 (udev)
Nov 17 11:39:18 | sda: detect_prio = 1 (config file default)
Nov 17 11:39:18 | sda: prio = const (controller setting)
Nov 17 11:39:18 | sda: prio args = (null) (controller setting)
Nov 17 11:39:18 | sda: const prio = 1
Nov 17 11:39:18 | sr0: device node name blacklisted
Nov 17 11:39:18 | dm-0: device node name blacklisted
Nov 17 11:39:18 | dm-1: device node name blacklisted
</cli>

For a complete list of the default configuration values, run:
<cli prompt='#'>
[root@BKPSRV1 etc]# multipath -t
</cli>

Then adapt your config file, and add the blacklist for local disk with no multipathing if needed: /etc/multipath.conf
<code>
...
blacklist {
      wwid SAIX_VDASD_000e583a0000d40000000143bb7850cf.17
      devnode "^(ram|raw|loop|fd|md|dm-|sr|scd|st)[0-9]*"
      devnode "^(td|hd)[a-z]"
}
</code>

Then restart multipathing:
<cli prompt='#'>
[root@BKPSRV1 etc]# systemctl reload multipathd.service
or 
[root@BKPSRV1 etc]# chkconfig multipathd reload
</cli>

Multipath command line:
<cli prompt='#'>
[root@BKPSRV1 etc]# multipathd -k
multipathd> ?
multipath-tools v0.4.9 (05/33, 2016)
CLI commands reference:
 list|show paths
 list|show paths format $format
 list|show status
 list|show daemon
 list|show maps|multipaths
 list|show maps|multipaths status
 list|show maps|multipaths stats
 list|show maps|multipaths format $format
 list|show maps|multipaths topology
 list|show topology
 list|show map|multipath $map topology
 list|show config
 list|show blacklist
 list|show devices
 list|show wildcards
 add path $path
 remove|del path $path
 add map|multipath $map
 remove|del map|multipath $map
 switch|switchgroup map|multipath $map group $group
 reconfigure
 suspend map|multipath $map
 resume map|multipath $map
 resize map|multipath $map
 reset map|multipath $map
 reload map|multipath $map
 disablequeueing map|multipath $map
 restorequeueing map|multipath $map
 disablequeueing maps|multipaths
 restorequeueing maps|multipaths
 reinstate path $path
 fail path $path
 quit|exit
 shutdown
 map|multipath $map getprstatus
 map|multipath $map setprstatus
 map|multipath $map unsetprstatus
 forcequeueing daemon
 restorequeueing daemon

multipathd> show paths
hcil    dev dev_t pri dm_st chk_st dev_st  next_check
0:0:1:0 sda 8:0   1   undef ready  running orphan    

multipathd> show paths
hcil    dev dev_t pri dm_st chk_st dev_st  next_check
0:0:1:0 sda 8:0   1   undef ready  running orphan    

multipathd> show devices
available block devices:
    sda devnode whitelisted, monitored
    sr0 devnode blacklisted, unmonitored
    dm-0 devnode blacklisted, unmonitored
    dm-1 devnode blacklisted, unmonitored
  
multipathd> show daemon
pid 24935 running
multipathd> 
</cli>


===== Multipathing per vendor =====

==== IBM 2145/flash ====

/etc/multipath.conf
<code>
     vendor "IBM"
     product "2145"
     path_grouping_policy "group_by_prio"
     path_selector "service-time 0" # Used by Red Hat 7.x
     prio "alua"
     path_checker "tur"
     failback "immediate"
     no_path_retry 5
     rr_weight uniform
     rr_min_io_rq "1"
     dev_loss_tmo 120	
</code>

**DM-MPIO for dev_loss_tmo**\\
After a problem is detected on an FC port and it set to infinity, the SCSI layer can wait until 2147483647 seconds (68 years) before removing it from the system. The default value is determined by the OS.

All Linux hosts should have a **dev_loss_tmo** setting, but the value in seconds is how long to wait for the device/paths to be pruned. The suggested duration is 120-150 seconds, but extended duration is also supported.

Care needs to be taken if it is too low since if paths are pruned, then they also need to be rediscovered and if too low, that may require manual rescan later. If inquiry timeout is right, the host should be able to re-add the paths when the SVC nodes are restored.

If the inquiry is too short such as 20 seconds then the inquiry may timeout before the paths are ready.

===== temporary =====

<cli prompt='#'>
# multipathd -k
multipathd> show multipaths status
name   failback  queueing paths dm-st  write_prot
mpathb immediate 18 chk   2     active rw
mpathf immediate 18 chk   2     active rw
mpathe immediate 18 chk   2     active rw
mpatha immediate 18 chk   2     active rw
mpathg -         -        2     active rw
mpathh -         -        2     active rw
mpathj -         -        2     active rw
mpathi -         -        2     active rw
</cli>




Add /etc/multipath.conf:
<code>
devices {
        device {
                vendor "HP"
                product "MSA 2040 SAS"
                path_grouping_policy group_by_prio
                getuid_callout "/lib/udev/scsi_id --whitelisted --device=/dev/%n"
                path_selector "round-robin 0"
                path_checker tur
                features "0"
                hardware_handler "0"
                prio alua
                failback immediate
                rr_weight uniform
                no_path_retry 18
                rr_min_io 100
                rr_min_io_rq 1
        }

}
</code>

Now:
<cli prompt='>'>
multipathd> show multipaths status
name   failback  queueing paths dm-st  write_prot
mpathb immediate 18 chk   2     active rw
mpatha immediate 18 chk   2     active rw
mpathe immediate 18 chk   2     active rw
mpathf immediate 18 chk   2     active rw
mpathh immediate 18 chk   2     active rw
mpathg immediate 18 chk   2     active rw
mpathj immediate 18 chk   2     active rw
mpathi immediate 18 chk   2     active rw
</cli>

===== Multipathing on OS disks =====

Install the multipath-tools and multipath-tools-boot packages

Installing OS with Multipath Support, example for Ubuntu\\
At the installer prompt
  install disk-detect/multipath/enable=true

If multipath devices are found these will show up as /dev/mapper/mpath<X> during installation.

https://help.ubuntu.com/lts/serverguide/multipath-admin-and-troubleshooting.html

===== remove multipathing device =====

<cli prompt='#'>
# dmsetup remove -f [map name]
# dmesetup remove -f 360060e80166bac0000016bac000000da
# multipath -f [LUN name]
# multipath -f 360060e80166bac0000016bac000000da
</cli>
=== Moving root File Systems from a Single Path Device to a Multipath Device ===

This is dramatically simplified by the use of UUIDs to identify devices as an intrinsic label. Simply install multipath-tools-boot and reboot. This will rebuild the initial ramdisk and afford multipath the opportunity to build it's paths before the root file system is mounted by UUID.

**Whenever multipath.conf is updated**, so should the initrd by executing 
  update-initramfs -u -k all
The reason being is multipath.conf is copied to the ramdisk and is integral to determining the available devices for grouping via it's blacklist and device sections.

=== Moving swap File Systems from a Single Path Device to a Multipath Device ===

The procedure is exactly the same as illustrated in the previous section called Moving root File Systems from a Single Path to a Multipath Device.

http://fibrevillage.com/storage/10-device-mapper-multipath-configuration-on-linux

https://www.thegeekdiary.com/how-to-rebuild-the-initramfs-with-multipath-in-centos-rhel-6-and-7/

https://access.redhat.com/solutions/3072701

https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/6/html/dm_multipath/move_root_to_multipath

https://access.redhat.com/discussions/2158911

https://access.redhat.com/solutions/3375911

https://access.redhat.com/solutions/65960

===== Error =====

<code>
WARNING: Not using lvmetad because duplicate PVs were found.
  WARNING: Use multipath or vgimportclone to resolve duplicate PVs?
  WARNING: After duplicates are resolved, run "pvscan --cache" to enable lvmetad.
  WARNING: PV xxxxxx-xxxx-xxxx-xxxx-xxxx-xxxx-xxxxx on /dev/sdx was already found on /dev/sdy.
  WARNING: PV xxxxxx-xxxx-xxxx-xxxx-xxxx-xxxx-xxxxx on /dev/sdy was already found on /dev/sdz.
  WARNING: PV xxxxxx-xxxx-xxxx-xxxx-xxxx-xxxx-xxxxx on /dev/sdz was already found on /dev/mapper/mpatha.
</code>

<code>
# cat /etc/lvm/lvm.conf | grep filter
filter = [ "a|/dev/mapper/mpath*|", "a|/dev/sdb3|", "r|.*|" ]
global_filter = [ "a|/dev/mapper/mpath*|", "a|/dev/sdb3|", "r|.*|" ]
</code>

==== Debug a filter ====

Use the followin command to find the right filter, and upadate the file /etc/lvm/lvm.conf:
<cli prompt='#'>
[root@redhat1:/etc/lvm/# pvs -a --config 'devices { filter = [ "a|.*|" ] }' --noheadings \
     -opv_name,fmt,vg_name | awk 'BEGIN { f = ""; } \
     NF == 3 { n = "\42a|"$1"|\42, "; f = f n; } END \
         { print "Suggested filter line for /etc/lvm/lvm.conf:\n \
         filter = [ "f"\"r|.*|\" ]" }'
         
  WARNING: Not using lvmetad because duplicate PVs were found.
  WARNING: Use multipath or vgimportclone to resolve duplicate PVs?
  WARNING: After duplicates are resolved, run "pvscan --cache" to enable lvmetad.
  WARNING: PV iLyQd5-vSRJ-k84X-Jpx8-Z3dM-k97W-xFV1kU on /dev/sdd3 was already found on /dev/sdb3.
  WARNING: PV iLyQd5-vSRJ-k84X-Jpx8-Z3dM-k97W-xFV1kU on /dev/sdf3 was already found on /dev/sdb3.
  WARNING: PV iLyQd5-vSRJ-k84X-Jpx8-Z3dM-k97W-xFV1kU on /dev/sdh3 was already found on /dev/sdb3.
  WARNING: PV iLyQd5-vSRJ-k84X-Jpx8-Z3dM-k97W-xFV1kU on /dev/sdj3 was already found on /dev/sdb3.
  WARNING: PV iLyQd5-vSRJ-k84X-Jpx8-Z3dM-k97W-xFV1kU on /dev/sdl3 was already found on /dev/sdb3.
  WARNING: PV iLyQd5-vSRJ-k84X-Jpx8-Z3dM-k97W-xFV1kU on /dev/sdn3 was already found on /dev/sdb3.
  WARNING: PV iLyQd5-vSRJ-k84X-Jpx8-Z3dM-k97W-xFV1kU on /dev/sdp3 was already found on /dev/sdb3.
  WARNING: PV iLyQd5-vSRJ-k84X-Jpx8-Z3dM-k97W-xFV1kU prefers device /dev/sdb3 because device is used by LV.
  WARNING: PV iLyQd5-vSRJ-k84X-Jpx8-Z3dM-k97W-xFV1kU prefers device /dev/sdb3 because device is used by LV.
  WARNING: PV iLyQd5-vSRJ-k84X-Jpx8-Z3dM-k97W-xFV1kU prefers device /dev/sdb3 because device is used by LV.
  WARNING: PV iLyQd5-vSRJ-k84X-Jpx8-Z3dM-k97W-xFV1kU prefers device /dev/sdb3 because device is used by LV.
  WARNING: PV iLyQd5-vSRJ-k84X-Jpx8-Z3dM-k97W-xFV1kU prefers device /dev/sdb3 because device is used by LV.
  WARNING: PV iLyQd5-vSRJ-k84X-Jpx8-Z3dM-k97W-xFV1kU prefers device /dev/sdb3 because device is used by LV.
  WARNING: PV iLyQd5-vSRJ-k84X-Jpx8-Z3dM-k97W-xFV1kU prefers device /dev/sdb3 because device is used by LV.
Suggested filter line for /etc/lvm/lvm.conf:
         filter = [ "a|/dev/mapper/mpatha|", "a|/dev/sdb3|", "a|/dev/sdd3|", "a|/dev/sdf3|", "a|/dev/sdh3|", "a|/dev/sdj3|", "a|/dev/sdl3|", "a|/dev/sdn3|", "a|/dev/sdp3|", "r|.*|" ]
         
[root@redhat1:/etc/lvm/# vi /etc/lvm/lvm.conf
</cli>


==== Remove a multipath device ====

Unable to remove the multipath device after unmapping the LUN from the server.

Attempting to flush a multipath map with "multipath -f" or "multipath -F" results in "map in use":
Raw

     # multipath -f mpath7
     mpath7: map in use

Resolution

    Locate any subsystem or process holding the multipath device open.  See diagnostic steps for possible tools and techniques.
    For any subsystem or process holding the multipath device open, stop the process, or issue commands to release the multipath device.

    Some examples of possible holders of a multipath device and the commands to release it:
        A filesystem exists on the multipath device and is currently mounted.
            Unmount the filesystem and if it exists in /etc/fstab, remove it.
        One or more partition mapping(s) still exists on the multipath device.
            Use "kpartx -d" on the multipath device to remove the device partition mapping(s).
        The multipath device was used by LVM, and still has device mapper state in the kernel.
        Use "lvchange -an" to deactivate any logical volume(s) associated with the multipath device.  A list of logical volumes associated with the multipath device may be found by examining the output of "lvs -o +devices".
        If "lvchange -an" fails, the logical volume is only partially removed, or there are blocked processes with I/O outstanding on the device, use "dmsetup remove -f" followed by "dmsetup clear" on the multipath device.  See dmsetup man page for full explanation of these commands.

    Once all holders of the device have been removed, the multipath device should be flushed with "multipath -f".

Root Cause

    The multipath device was held open by at least one process or subsystem.

Check with
    Use 'lsof' to attempt to find anyone holding the device open.
    Check 'dmsetup' output for any device mapper maps that depend on the multipath device
    Check the if there is a device for mpath7 in /dev/mapper/mpath7
    Check multipath -v4 -ll

==== Multipathing error ====

Path offline
<cli prompt='#'>
[root@lnxa087 scripts]# /usr/sbin/multipath -ll
mpatha (36005076801818664680000000000062d) dm-0 IBM     ,2145
size=40G features='1 queue_if_no_path' hwhandler='0' wp=rw
|-+- policy='service-time 0' prio=0 status=enabled
| |- 1:0:2:0 sdb 8:16  failed faulty offline
| |- 2:0:2:0 sdh 8:112 failed faulty offline
| |- 3:0:2:0 sde 8:64  failed faulty offline
| `- 4:0:2:0 sdg 8:96  failed faulty offline
`-+- policy='service-time 0' prio=10 status=active
  |- 1:0:0:0 sda 8:0   active ready running
  |- 2:0:0:0 sdc 8:32  active ready running
  |- 3:0:0:0 sdd 8:48  active ready running
  `- 4:0:0:0 sdf 8:80  active ready running
[root@lnxa087 scripts]# pvs
  /dev/sdb: open failed: No such device or address
  /dev/sde: open failed: No such device or address
  /dev/sdg: open failed: No such device or address
  /dev/sdh: open failed: No such device or address
  PV                  VG     Fmt  Attr PSize  PFree
  /dev/mapper/mpatha3 centos lvm2 a--  38.99g    0
</cli>

First try to rescan:
<cli prompt='#'>
[root@lnxa087 scripts]# for i in $(ls /sys/class/scsi_host/host*/scan); do echo "- - -" > $i; done
</cli>

If not success, check adapter status (required **sysfsutils** package)
<cli prompt='#'>
[root@lnxa087 etc]# systool -c fc_host -v
Class = "fc_host"

  Class Device = "host1"
  Class Device path = "/sys/devices/vio/30000004/host1/fc_host/host1"
    dev_loss_tmo        = "300"
    fabric_name         = "0xc0507608249e00ac"
    issue_lip           = <store method only>
    maxframe_size       = "2048 bytes"
    node_name           = "0xc0507608249e00ac"
    port_id             = "0xbf1b13"
    port_name           = "0xc0507608249e00ac"
    port_state          = "Online"
    port_type           = "NPIV VPORT"
    speed               = "8 Gbit"
    supported_classes   = "Class 2, Class 3"
    tgtid_bind_type     = "wwpn (World Wide Port Name)"
    uevent              =

    Device = "host1"
    Device path = "/sys/devices/vio/30000004/host1"
      uevent              = "DEVTYPE=scsi_host"
...
</cli>

If adapters OK, the remove failed paths:
<cli prompt='#'>
[root@lnxa087 etc]# rescan-scsi-bus.sh -r
</cli>

Rescan
<cli prompt='#'>
[root@lnxa087 etc]# sg_map -x
/dev/sg1  1 0 0 0  0  /dev/sda
/dev/sg3  2 0 0 0  0  /dev/sdc
/dev/sg4  3 0 0 0  0  /dev/sdd
/dev/sg6  4 0 0 0  0  /dev/sdf
[root@lnxa087 scripts]# for i in $(ls /sys/class/scsi_host/host*/scan); do echo "- - -" > $i; done
</cli>

Check again:
<cli prompt='#'>
[root@lnxa087 etc]# [root@lnxa087 etc]# sg_map -x
/dev/sg0  1 0 2 0  0  /dev/sdb
/dev/sg1  1 0 0 0  0  /dev/sda
/dev/sg2  2 0 2 0  0  /dev/sde
/dev/sg3  2 0 0 0  0  /dev/sdc
/dev/sg4  3 0 0 0  0  /dev/sdd
/dev/sg5  3 0 2 0  0  /dev/sdg
/dev/sg6  4 0 0 0  0  /dev/sdf
/dev/sg7  4 0 2 0  0  /dev/sdh
[root@lnxa087 etc]# /usr/sbin/multipath -ll
mpatha (36005076801818664680000000000062d) dm-0 IBM     ,2145
size=40G features='1 queue_if_no_path' hwhandler='0' wp=rw
|-+- policy='service-time 0' prio=50 status=active
| |- 1:0:2:0 sdb 8:16  active ready running
| |- 2:0:2:0 sde 8:64  active ready running
| |- 3:0:2:0 sdg 8:96  active ready running
| `- 4:0:2:0 sdh 8:112 active ready running
`-+- policy='service-time 0' prio=10 status=enabled
  |- 1:0:0:0 sda 8:0   active ready running
  |- 2:0:0:0 sdc 8:32  active ready running
  |- 3:0:0:0 sdd 8:48  active ready running
  `- 4:0:0:0 sdf 8:80  active ready running
</cli>

==== PV not found ====

Path offline
<cli prompt='#'>
[root@linux01]/usr/bin # vgs
  WARNING: Device for PV nNtH6F-Ppre-ROWM-DH8e-vrHe-8f08-PJHMjO not found or rejected by a filter.
  WARNING: Device for PV yCgOKm-oDZO-lSns-11fT-K11G-1025-xEHww2 not found or rejected by a filter.
    WARNING: Device for PV nNtH6F-Ppre-ROWM-DH8e-vrHe-8f08-PJHMjO not found or rejected by a filter.
  Couldn't find device with uuid nNtH6F-Ppre-ROWM-DH8e-vrHe-8f08-PJHMjO.
</cli>

Ceanup config using
<cli prompt='#'>
[root@linux01]/usr/bin # pvscan --cache
[root@linux01]/usr/bin # pvscan
</cli>
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