Bug 1122146

Summary: Growing linear RAID array causes error "cannot understand this RAID level"
Product: [Fedora] Fedora Reporter: mulhern <amulhern>
Component: mdadmAssignee: Jes Sorensen <Jes.Sorensen>
Status: CLOSED ERRATA QA Contact: Fedora Extras Quality Assurance <extras-qa>
Severity: unspecified Docs Contact:
Priority: unspecified    
Version: 20CC: agk, amulhern, dledford, Jes.Sorensen
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Fixed In Version: mdadm-3.3-7.fc20 Doc Type: Bug Fix
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Last Closed: 2014-08-15 02:51:05 UTC Type: Bug
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Information requested none

Description mulhern 2014-07-22 16:00:26 UTC 
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):

3.3

How reproducible:

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>"

Actual results:

"cannot understand this RAID level" error message

Expected results:

Array is grown or more upbeat message something like
"mdadm: ddf metadata does not support reshape"

Additional info:

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
EVENTS: 0
FAILED DEVICES: 0
NAME: localhost.localdomain:0  (local to host localhost.localdomain)
PERSISTENCE: Superblock is persistent
RAID DEVICES: 2
RAID LEVEL: linear
ROUNDING: 0K
SPARE DEVICES: 0
STATE: clean
TOTAL DEVICES: 2
UPDATE TIME: Tue Jul 22 11:27:11 2014
UUID: f240dfa0-a97e-1012-adfe-772006af61f9
VERSION: 1.2
WORKING DEVICES: 2

This is through the testing structure, so the formatting of the output is
not as mddetail would have it.
Comment 1 Jes Sorensen 2014-07-22 16:16:28 UTC 
Please provide 'cat /proc/mdstat' and 'mdadm --detail /dev/md<X>' output.
Comment 2 mulhern 2014-07-22 19:25:57 UTC 
Created attachment 920037 [details]
Information requested

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.
Comment 3 Jes Sorensen 2014-07-23 14:17:18 UTC 
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.

Jes
Comment 4 mulhern 2014-07-24 15:05:27 UTC 
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.
Comment 5 Jes Sorensen 2014-07-24 15:54:41 UTC 
Not correct, after investigation, it's the fact you cannot use -n with linear
arrays. 

Try something like this: 
mdadm /dev/md<X> -G -a /dev/sd<Y>
Comment 6 Fedora Update System 2014-07-29 10:54:26 UTC 
mdadm-3.3-7.fc20 has been submitted as an update for Fedora 20.
https://admin.fedoraproject.org/updates/mdadm-3.3-7.fc20
Comment 7 Fedora Update System 2014-07-30 06:56:09 UTC 
Package mdadm-3.3-7.fc20:
* 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:
https://admin.fedoraproject.org/updates/FEDORA-2014-8956/mdadm-3.3-7.fc20
then log in and leave karma (feedback).
Comment 8 Fedora Update System 2014-08-15 02:51:05 UTC 
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.