Bugreport: mdmon will not start with latest git version when using ddf container

Seems mdmon will not start when I create a ddf container with raid devices therein:

I am using this version from git:

mdadm - v3.3-rc2-20-gd81cc6a - 31st July 2013

on Centos 6.4, 2.6.32-358.14.1.el6.x86_64

I am using 5 loop devices of 512 MB each for disks. I created a container with 5 disks:

mdadm -CR /dev/md127 -e ddf -l container -n 5 /dev/loop[1-5]

[root@moonlight ~]# cat /proc/mdstat
Personalities : [raid6] [raid5] [raid4] [raid1]
md127 : inactive loop5[4](S) loop4[3](S) loop3[2](S) loop2[1](S) loop1[0](S)
163840 blocks super external:ddf

unused devices: <none>

And created two raid sets in it, one with three disks in raid 5, the other a raid 1

[root@moonlight ~]# mdadm -CR /dev/md1 -l raid5 -n 3 /dev/md127
mdadm: array /dev/md1 started.
mdadm: failed to launch mdmon. Array remains readonly [root@moonlight ~]# cat /proc/mdstat
Personalities : [raid6] [raid5] [raid4] [raid1]
md1 : active (read-only) raid5 loop1[2] loop2[1] loop3[0]

      958464 blocks super external:/md127/1 level 5, 512k chunk, 

algorithm 2 [3/3] [UUU]
resync=PENDING

md0 : active (read-only) raid1 loop4[1] loop5[0]

      479232 blocks super external:/md127/0 [2/2] [UU]
          resync=PENDING

md127 : inactive loop5[4](S) loop4[3](S) loop3[2](S) loop2[1](S) loop1[0](S)
163840 blocks super external:ddf

unused devices: <none>

And adding another one, raid5 in my case, gives the same result for the next /dev/md device.

Unfortunately, they stay readonly, as mdmon won't start, so mdadm --readwrite /dev/md0, etc, won't work.

However, when I create these raid devices directly on top of the /dev/loop[1-5] devices, without using a ddf container, it works as advertised and the devices get (re)build/resynced.

Regards,

Albert

Thanks for the report.
This works when I try it so we must be doing something slightly differently.

When mdadm tries to run mdmon it looks in:
- the same directory that 'mdadm' was found in
- /sbin
- the current directory.

Where are mdadm and mdmon installed? What directory are you running from. If we can't discover the problem from that information, please run
strace -f -o /tmp/md-trace mdadm -CR /dev/md1 -l raid5 -n 3 /dev/md127

and post the resulting /tmp/md-trace file.

Thanks,
NeilBrown

Yes I can.

mdmon needs to create /run/mdadm but you don't have '/run'. try:
make clean
make MAP_DIR=/var/run/mdadm
or maybe
make MAP_DIR=/dev/.mdadm

NeilBrown

I believe that most distros are moving towards /run so I think that is the best default.
I guess I could get the Makefile to check that the chosen directory exists...

NeilBrown

I rather not do too much guessing..
For now I've changed the Makefile so that if the relevant directory doesn't exist it will fail and tell you how to avoid the failure.

Thanks,
NeilBrown