mdadm is not able to create a RAID6 with 3 disks in degraded mode

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Environment

SUSE Linux Enterprise Server 10
SUSE Linux Enterprise Desktop 10

Situation

You are trying to use the following command

mdadm --create /dev/md0 --level=6 --chunk=128 --raid-devices=4 disk1 disk2 disk3 missing

to create a RAID6 with 3 disks. The command exits with the following error messages
ERROR:

mdadm: RUN_ARRAY failed: Input/output error
mdadm: stopped /dev/md0

Resolution

The problem is reported to engineering and update for mdadm will be published as soon as fixed.

Workaround

First create a RAID6 with 2 disks

mdadm --create /dev/md0 --level=6 --chunk=128 --raid-devices=4 disk1 disk2 missing missing

and then add the 3rd disk

mdadm /dev/md0 --manage -a disk3

Disclaimer

This Support Knowledgebase provides a valuable tool for SUSE customers and parties interested in our products and solutions to acquire information, ideas and learn from one another. Materials are provided for informational, personal or non-commercial use within your organization and are presented "AS IS" WITHOUT WARRANTY OF ANY KIND.