Degraded array not assembled via mdadm.conf?

[Barry Tennison]

I find mdadm a superb collection of tools - many thanks for all the work!

I'm posting just one thing that puzzles me.  For this issue, I'm running 
squeeze/testing on armv5tel (orion5) and have mdadm version 3.0-3.1

I have a degraded RAID1 array, with one active drive and one failed, removed 
drive.  This "array" assembles and runs fine with the manual command
   mdadm -A -u <correct UUID> /dev/md1
For the time being, I want to continue to use this array in degraded form, and 
have it auto-run at boot time.

However, when I put the any of the following lines in /etc/mdadm/mdadm.conf
  ARRAY /dev/md1 num-devices=2 UUID=<correct UUID>
  ARRAY /dev/md1 num-devices=1 UUID=<correct UUID>
  ARRAY /dev/md1 UUID=<correct UUID>
the array fails to assemble at boot.  The message in syslog is (always)
  mdadm[1336]: DegradedArray event detected on md device /dev/md1

I have got around this by putting the "manual" commands
  mdadm -A -u <correct UUID> /dev/md1
  mount /dev/md1
in rc.local, and now the array assembles, runs and is mounted fine.

I'm not sure whether this is a bug or a feature.  Is there a rationale for the 
difference between the results of attempting the same thing in mdadm.conf and 
"manually" in rc.local?

Thanks again for all the great work.

Barry