[Bug 551719] [NEW] enabled kernel raid autodetection disturbs udev/mdadm (initramfs & later)

[ceg]

Public bug reported:


Ubuntu's current kernel option
CONFIG_MD_AUTODETECT=y
enables the kernel's RAID autodetection during boot.

Aside from causing a delay for everyone this often also disturbs the udev/mdadm setup of raid devices in the system.
(i.e. devices partly busy/set up without an entry in the mapfile used by mdadm --incremental)

Here is what README.initrams from mdadm tarball says about the kernel's
raid autodetection feature:

"while useful, [they] do not provide complete functionality
and are unlikely to be extended.  The preferred way to assemble md
arrays at boot time is using 'mdadm' "

Ubuntu does this using udev rules in initramfs as well as later on.

The kernel's raid autodetection should therefore be disabled in ubuntu
kernels.

** Affects: linux (Ubuntu)
     Importance: Undecided
         Status: New

** Affects: mdadm (Ubuntu)
     Importance: Undecided
         Status: New

** Also affects: linux (Ubuntu)
   Importance: Undecided
       Status: New

** Description changed:

- Binary package hint: mdadm
  
- 
- Ubutus current kernel option
+ Ubuntu's current kernel option
  CONFIG_MD_AUTODETECT=y
  enables the kernel's RAID autodetection during boot.
  
  Aside from causing a delay for everyone this often also disturbs the udev/mdadm setup of raid devices in the system.
  (i.e. devices partly busy/set up without an entry in the mapfile used by mdadm --incremental)
  
  Here is what README.initrams from mdadm tarball says about the kernel's
  raid autodetection feature:
  
  "while useful, [they] do not provide complete functionality
  and are unlikely to be extended.  The preferred way to assemble md
  arrays at boot time is using 'mdadm' "
  
  Ubuntu does this using udev rules in initramfs as well as later on.
  
  The kernel's raid autodetection should therefore be disabled in ubuntu
  kernels.

-- 
enabled kernel raid autodetection disturbs udev/mdadm (initramfs & later)
https://bugs.launchpad.net/bugs/551719
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