Why does kernel upgrade break multipath on Boot-from-San system ?

Issue

• Server was installed using kickstart from RHN Satellite RHELv6.1.1 kickstart template as boot-from-SAN. When the kernel was upgraded and the system was rebooted, the multipah device from which the system was booting disappeared and the paths to the LUN were broken / splitted. Rebuilding the system with a fresh kickstart profile and doing a 'yum update' excluding the kernel, worked without any issues. When the kernel was upgraded the issue resurfaced.

  The multipath_-v4_-ll file in pre-update:
  
  ===== paths list =====
  uuid hcil    dev dev_t pri dm_st chk_st vend/prod/rev       dev_st
       2:0:1:0 sdc 8:32  -1  undef ready  NETAPP,LUN          running
       2:0:2:0 sdd 8:48  -1  undef ready  NETAPP,LUN          running
       3:0:2:0 sde 8:64  -1  undef ready  NETAPP,LUN          running
       3:0:3:0 sdf 8:80  -1  undef ready  NETAPP,LUN          running
  ......
  mpathc (360a98000486e64674b4a6752626f5844) dm-0 NETAPP,LUN
  size=100G features='0' hwhandler='0' wp=rw
  `-+- policy='round-robin 0' prio=30 status=active
    |- 2:0:1:0 sdc 8:32 active ready running
    |- 2:0:2:0 sdd 8:48 active ready running
    |- 3:0:2:0 sde 8:64 active ready running
    `- 3:0:3:0 sdf 8:80 active ready running
  
  
  The multipath_-v4_-ll file in post-update:
  ===== paths list =====
  uuid hcil    dev dev_t pri dm_st chk_st vend/prod/rev         dev_st
       2:0:1:0 sdc 8:32  -1  undef ready  NETAPP,LUN            running
       2:0:2:0 sdd 8:48  -1  undef ready  NETAPP,LUN            running
       3:0:3:0 sdf 8:80  -1  undef ready  NETAPP,LUN            running
       3:0:2:0 sde 8:64  -1  undef ready  NETAPP,LUN            running
  
  
  No multipath device is seen, only underlying devices are seen
  
       2:0:1:0 sdc 8:32  -1  undef ready  NETAPP,LUN            running
       2:0:2:0 sdd 8:48  -1  undef ready  NETAPP,LUN            running
       3:0:3:0 sdf 8:80  -1  undef ready  NETAPP,LUN            running
       3:0:2:0 sde 8:64  -1  undef ready  NETAPP,LUN            running
  
  Four underlying devices on both pre-update and post-update can be seen. However mpathc disappears on post-update, the underlying devices don't coalesce.