Description of problem:
Attempting to grow linear array from 2 to 3 using command "mdadm --grow <array> --raid-devices 3 "--add <device>" results in failure and error message "cannot understand this RAID level"
Version-Release number of selected component (if applicable):
Always (through a testing infrastructure on top of loop devices)
Steps to Reproduce:
1. Create the array as "mdadm --create <array> --run --level=linear --raid-devices=2 <dev1> <dev2>
2. Grow the array as "mdadm --grow <array> --raid-devices 3 "--add <device>"
"cannot understand this RAID level" error message
Array is grown or more upbeat message something like
"mdadm: ddf metadata does not support reshape"
mddetail returns the following information on the array just before the grow call,
ACTIVE DEVICES: 2
ARRAY SIZE: 204640 (199.88 MiB 209.55 MB)
CREATION TIME: Tue Jul 22 11:27:11 2014
FAILED DEVICES: 0
NAME: localhost.localdomain:0 (local to host localhost.localdomain)
PERSISTENCE: Superblock is persistent
RAID DEVICES: 2
RAID LEVEL: linear
SPARE DEVICES: 0
TOTAL DEVICES: 2
UPDATE TIME: Tue Jul 22 11:27:11 2014
WORKING DEVICES: 2
This is through the testing structure, so the formatting of the output is
not as mddetail would have it.
Please provide 'cat /proc/mdstat' and 'mdadm --detail /dev/md<X>' output.
Created attachment 920037 [details]
The attached file contains the information requested which was obtained immediately after creation of the array and just before the attempt to grow the array, adding an additional device. Note that it was obtained from within the Python debugger.
I can reproduce this, however it looks to be a very long standing bug, as
the same happens with mdadm-3.2.6.
I am not sure if growing a linear array is even supported in the first place,
I will need to investigate this.
It is also not possible to use --add to add a new disk to an existing linear array. AFAIK, this means that increasing the size of a linear array after it has been created is impossible.
Not correct, after investigation, it's the fact you cannot use -n with linear
Try something like this:
mdadm /dev/md<X> -G -a /dev/sd<Y>
mdadm-3.3-7.fc20 has been submitted as an update for Fedora 20.
* should fix your issue,
* was pushed to the Fedora 20 testing repository,
* should be available at your local mirror within two days.
Update it with:
# su -c 'yum update --enablerepo=updates-testing mdadm-3.3-7.fc20'
as soon as you are able to.
Please go to the following url:
then log in and leave karma (feedback).
mdadm-3.3-7.fc20 has been pushed to the Fedora 20 stable repository. If problems still persist, please make note of it in this bug report.