Partitions on `sd` devices are not getting detected in RHEL6/7 after reboot when multipathd is used

Issue

• When we create partition on multipath device, partitions on underlying sd devices are seen missing.

• Partitions on /dev/sd devices are not getting detected after reboot.

• Multipath devices:

mpathc (36000d310000065000000000000001f0f) dm-0 COMPELNT,Compellent Vol  
size=1.0G features='1 queue_if_no_path' hwhandler='0' wp=rw
`-+- policy='service-time 0' prio=1 status=active
  |- 0:0:5:2 sdf 8:80  active ready running
  |- 0:0:6:2 sdg 8:96  active ready running
  |- 7:0:4:2 sdl 8:176 active ready running
  `- 7:0:6:2 sdm 8:192 active ready running

• Multipath device links:

lrwxrwxrwx. 1 0 0  10 Feb 13 16:21 dm-name-mpathc -> ../../dm-0
lrwxrwxrwx. 1 0 0  10 Feb 13 16:21 dm-name-mpathc1 -> ../../dm-1

• Underlying multipath devices:

# cat proc/partitions |egrep "sdf|sdg|sdl|sdm"
   8       80    1048576 sdf
   8       96    1048576 sdg
   8      176    1048576 sdl
   8      192    1048576 sdm

• Device list in /dev directory:

# less sos_commands/block/ls_-lanR_.dev |egrep "sdf|sdg|sdl|sdm"

brw-rw----.  1 0  6   8,  80 Feb 13 16:21 sdf
brw-rw----.  1 0  6   8,  96 Feb 13 16:21 sdg
brw-rw----.  1 0  6   8, 176 Feb 13 16:21 sdl
brw-rw----.  1 0  6   8, 192 Feb 13 16:21 sdm
lrwxrwxrwx.  1 0 0    6 Feb 13 16:21 8:176 -> ../sdl
lrwxrwxrwx.  1 0 0    6 Feb 13 16:21 8:192 -> ../sdm
lrwxrwxrwx.  1 0 0    6 Feb 13 16:21 8:80 -> ../sdf
lrwxrwxrwx.  1 0 0    6 Feb 13 16:21 8:96 -> ../sdg
lrwxrwxrwx. 1 0 0   9 Feb 13 16:21 scsi-36000d310000065000000000000001f0f -> ../../sdm
lrwxrwxrwx. 1 0 0   9 Feb 13 16:21 wwn-0x6000d310000065000000000000001f0f -> ../../sdf
lrwxrwxrwx. 1 0 0   9 Feb 13 16:21 pci-0000:41:00.0-fc-0x5000d31000006505-lun-2 -> ../../sdg
lrwxrwxrwx. 1 0 0   9 Feb 13 16:21 pci-0000:41:00.0-fc-0x5000d31000006506-lun-2 -> ../../sdf
lrwxrwxrwx. 1 0 0   9 Feb 13 16:21 pci-0000:41:00.1-fc-0x5000d31000006507-lun-2 -> ../../sdm
lrwxrwxrwx. 1 0 0   9 Feb 13 16:21 pci-0000:41:00.1-fc-0x5000d31000006508-lun-2 -> ../../sdl

• However partitions are getting detected as showed in the following command outputs:

  • fdisk:

  # cat sos_commands/block/fdisk_-l_.dev.sdf 
  
  Disk /dev/sdf: 1073 MB, 1073741824 bytes, 2097152 sectors
  Units = sectors of 1 * 512 = 512 bytes
  Sector size (logical/physical): 512 bytes / 512 bytes
  I/O size (minimum/optimal): 2097152 bytes / 2097152 bytes
  Disk label type: dos
  Disk identifier: 0xef3441e5
  
  Device Boot      Start         End      Blocks   Id  System
  /dev/sdf1            4096     2097151     1046528   83  Linux
  

  • parted:

  # cat sos_commands/block/parted_-s_.dev.sdf_print 
  Model: COMPELNT Compellent Vol (scsi)
  Disk /dev/sdf: 1074MB
  Sector size (logical/physical): 512B/512B
  Partition Table: msdos
  Disk Flags: 
  
  Number  Start   End     Size    Type     File system  Flags
  1      2097kB  1074MB  1072MB  primary
  

  • dmesg:

  # sos_commands/kernel/dmesg
  
  [    5.145014]  sdg: sdg1
  [    5.145797] sd 0:0:6:2: [sdg] Attached SCSI disk
  [    5.151472]  sdf: sdf1
  [    5.152291] sd 0:0:5:2: [sdf] Attached SCSI disk
  [    7.719176] sd 7:0:4:2: [sdl] 2097152 512-byte logical blocks: (1.07 GB/1.00 GiB)
  [    7.719620] sd 7:0:4:2: [sdl] Write Protect is off
  [    7.719622] sd 7:0:4:2: [sdl] Mode Sense: 8f 00 00 08
  [    7.719735] sd 7:0:4:2: [sdl] Write cache: disabled, read cache: enabled, doesn't support DPO or FUA
  [    7.723910] sd 7:0:6:2: [sdm] 2097152 512-byte logical blocks: (1.07 GB/1.00 GiB)
  [    7.724320] sd 7:0:6:2: [sdm] Write Protect is off
  [    7.724322] sd 7:0:6:2: [sdm] Mode Sense: 8f 00 00 08
  [    7.724434] sd 7:0:6:2: [sdm] Write cache: disabled, read cache: enabled, doesn't support DPO or FUA
  [    7.734991]  sdm: sdm1
  [    7.735803] sd 7:0:6:2: [sdm] Attached SCSI disk
  [    7.745098]  sdl: sdl1
  

  • /var/log/messages logs:

  Feb 13 16:21:08 ora5 kernel: sdf: sdf1