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

[ceg]

** Description changed:

+ Ubuntu still uses the kernel option
+ CONFIG_MD_AUTODETECT=y
+ thus enables the kernel's RAID autodetection during boot.
  
- 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)
+ However, aside from causing a delay for everyone, this often also disturbs the udev/mdadm setup when raid devices are present in the system.
+ (i.e. devices are partly busy/set up by the kernel, 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:
+ raid autodetection features:
  
  "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.
+ Ubuntu does assemble arrays using udev rules that run mdadm. (In
+ initramfs as well as later on.)
  
- The kernel's raid autodetection should therefore be disabled in ubuntu
- kernels.
+ The kernel's raid autodetection can and 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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