Red Hat Bugzilla – Bug 132706
[RFE] mdadm could create raid devices that don't exist
Last modified: 2007-11-30 17:10:49 EST
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Description of problem:
With udev, creating new raid devices is a bit of a pain, since the
device nodes are not there. It would be nice if mdadm would create
them when given the -m number flag (or even infer the minor number
from the /dev/md%i pattern), if the named devices don't exist.
Version-Release number of selected component (if applicable):
Steps to Reproduce:
1.mdadm -C /dev/md4 -n 1 -l 2 /dev/hdx1 /dev/hdy1
Actual Results: /dev/md4 does not exist
Expected Results: Before udev, we had plenty of raid devices already
present in /dev, and this just worked. I wish it would work again.
This is solved with mdadm-1.9.0-3. Use the --auto=md flag to create a regular
md device file if it doesn't exist or use the --auto=mdp flag to create a
partitionable md device if it doesn't exist (but you have to use a name other
than /dev/md* when using partitionable devices, for example I created a 16
partition md device on an external FC array using this command:
[root@pe-fc4 ~]# mdadm -C /dev/fcarray -l 5 -n 4 --auto=mdp16 /dev/md0 /dev/md1
note that I used stacked md devices, and there are some bugs in stacked md
device handling in the mdadm-1.9.0 package, specifically it doesn't do mdadm -E
properly on stacked devices, but it does start them OK).
I don't think the need for --auto=md is, well, auto enough. If you're using one
of the standard device name, I can't think of any reason to not go ahead and
create the device if it's not there, since all the info can be inferred from the
I changed the default setting of auto= to do as you wish. As of
mdadm-1.11.0-2.fc4 in dist-FC4-HEAD this now works the way you want.