Boot with a degraded raid 5

Phillip Susi psusi at
Tue Dec 4 20:47:55 UTC 2007

ben.div wrote:
> Woh ! Absolutely nobody can help me on this question ? I've already 
> asked about this on 4-5 lists or forums, and I've cumulated : 0 answer.
> Where could I find help on this subject ? The kernel team ? Who has 
> developped this part (boot on initramfs and device detection) ?
> I'm stucked on that problem since 2 weeks. Please, help :)

Known issue... though I can't seem to find the bug # now.

> Ben Ben a écrit :
>> So here, I suspected that the wrong option was passed to mdadm in
>> initramfs, and tell it to not to run a degraded array.
>> I've found (with grep on initrams content) that the file
>> /etc/udev/rules.d/85-mdadm.rules contains this line :
>> SUBSYSTEM=="block", ACTION=="add|change", ENV{ID_FS_TYPE}=="linux_raid*", \
>>         RUN+="watershed /sbin/mdadm --assemble --scan --no-degraded"
>> I guess it's the boot parameter for mdadm ! So, I changed it, made a new
>> initramfs, reboot with only 2 disks and... nothing more, it doesn't
>> start anymore :/

Not sure what's going wrong without any description other than "it 
doesn't start anymore", but that should allow you to boot in a degraded 

>> So, after this long story (sorry), my questions :
>> Do you think I'm totally lost, or editing this file is the good way ?
>> Is there a good reason why ubuntu's dev chose this "--no-degraded"
>> option for mdadm by default ?
>> What can I do more ??

The reason is because we don't want to degrade an array just because one 
of the disks has not been detected yet.  The proper solution is to wait 
for either a timeout or manual intervention to go ahead and mount the 
array degraded.

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