Re: mdadm does not create partition devices whatsoever, "partitionable" functionality broken

[Christopher White <linux@pulseforce.com>]

I forgot to mention that I've also tried "sudo fdisk /dev/md1" and 
creating two partitions that way. It fails too.

This leads me to conclude that /dev/md1 was never created in 
partitionable mode and that the kernel refuses to create anything beyond 
a single partition on it.

On 5/13/11 7:18 PM, Christopher White wrote:
> Hi Phil, thanks for the response!
>
> On 5/13/11 6:49 PM, Phil Turmel wrote:
>> Hi Christopher,
>>
>> On 05/13/2011 11:13 AM, Christopher White wrote:
>>> Greetings.
>>>
>>> I have spent TEN hours trying everything other than regressing to a 
>>> REALLY old version. I started out on 3.1.4 and have also tried 
>>> manually upgrading to 3.2.1, but the bug still exists.
>>>
>>> Somewhere along the way, the "auto" partitionable flag has broken.
>>>
>>> sudo mdadm --create --level=raid5 --auto=part2 /dev/md1 
>>> --metadata=1.2 --raid-devices=4 /dev/sda2 /dev/sdb2 /dev/sdc2 /dev/sdd2
>>>
>>> This only creates /dev/md1. It is of course possible to create one 
>>> big partition as /dev/md1p1 with any partitioning program, but 
>>> FORGET about trying to create /dev/md1p2.
>> What exactly did fdisk or parted report when you tried to partition 
>> /dev/md1 ?
> I run "sudo gparted /dev/md1" to access the whole RAID array, since I 
> like the GUI for precisely creating partitions. When making two ext4 
> partitions and applying the changes, it successfully creates 
> /dev/md1p1 (which does not exist before this operation is performed). 
> It then goes on to trying to create md1p2 and it sends the commands to 
> the md1 device, but md1p2 is never created. After the step of creating 
> the partition (which failed, but gparted does not know that), it tries 
> to set up the file system, which fails since there is no md1p2:
> mkfs.ext4 -j -O extent -L "" /dev/md1p2
> "mke2fs 1.41.14 (22-Dec-2010)
> Could not stat /dev/md1p2 --- No such file or directory"
>>> The problem is that the RAID array is NOT created in partitionable 
>>> mode, and only supports one large partition, despite ALL attempts at 
>>> EVERY format of the --auto option, you name it, -a part2, 
>>> --auto=mdp2, --auto=part2, --auto=p2, --auto=mdp, --auto=part, 
>>> --auto=p, --auto=p4, you name it and I've tried it!
>>>
>>> My guess is the functionality of creating partitionable arrays 
>>> literally DID break somewhere prior to/at version 3.1.4 which is the 
>>> earliest version I tried.
>> The mdadm<==>  kernel interface for this might be broken, but as a 
>> side-effect of the change to make all md devices support conventional 
>> partition tables.  I don't recall exactly when this changed, but it 
>> was several kernels ago.
>>
>> What kernel are you running?
> Linux Mint 11 RC, which uses 2.6.38-8-generic.
>>> I'm giving up and creating physical n-1 sized partitions on the 
>>> source disks and creating two RAID 5 arrays from those partitions 
>>> instead, but decided I really MUST report this bug so that other 
>>> people don't bang their head against the wall for ten hours of their 
>>> life as well. ;-)
>> Consider trying "mdadm --create" without the "--auto" option at all, 
>> then fdisk on the resulting array.
>>
>> Phil
> I've tried that as well during my testing since some postings 
> suggested that leaving out the option will create a partitionable 
> array, but it didn't.
>
>
> Christopher