RAID 0 with 3 disks: md/raid0: please set raid.default_layout to 1 or 2
Monday, November 25 2019 · Lesezeit: 2 Minuten · 380 Wörter Achtung! Dieser Artikel ist älter als ein Jahr. Der Inhalt ist möglicherweise nicht mehr aktuell!Today was time for a backup. I’ve recently increased my RAID 0 with a third disk for more space. Adding the disk was already a pain in the ass and it seemed that I fucked up again. Last time I did a backup was round about a month ago. So today I attached the three disks again and the RAID would not build. A mdadm --detail
gave me:
[root@homeserver ~]# mdadm --detail /dev/md127
/dev/md127:
Version : 1.2
Creation Time : Mon Oct 7 18:11:26 2019
Raid Level : raid0
Raid Devices : 3
Total Devices : 3
Persistence : Superblock is persistent
Update Time : Mon Oct 7 18:11:26 2019
State : active, FAILED, Not Started
Active Devices : 3
Working Devices : 3
Failed Devices : 0
Spare Devices : 0
Chunk Size : 512K
Consistency Policy : unknown
Number Major Minor RaidDevice State
- 0 0 0 removed
- 0 0 1 removed
- 0 0 2 removed
That’s nasty. When I tried to assemble no error appeared on scree. But dmesg logged something:
[869705.131868] sd 15:0:0:0: [sdm] Attached SCSI disk
[869705.248265] md127: ADD_NEW_DISK not supported
[870085.207371] md: md127 stopped.
[870260.516069] md: md127 stopped.
[870260.523859] md/raid0:md127: cannot assemble multi-zone RAID0 with default_layout setting
[870260.523861] md/raid0: please set raid.default_layout to 1 or 2
Thankfully some people on the internet (🖇️ 🔐) digged into the C code and found a solution:
- First stop the RAID 0:
mdadm --stop /dev/md12
- Do magic:
echo 2 > /sys/module/raid0/parameters/default_layout
- Assembly the RAID 0:
mdadm --assemble /dev/md127
After that the detail page looks promising:
[root@homeserver ~]# mdadm --detail /dev/md127
/dev/md127:
Version : 1.2
Creation Time : Mon Oct 7 18:11:26 2019
Raid Level : raid0
Array Size : 8790295552 (8383.08 GiB 9001.26 GB)
Raid Devices : 3
Total Devices : 3
Persistence : Superblock is persistent
Update Time : Mon Oct 7 18:11:26 2019
State : clean
Active Devices : 3
Working Devices : 3
Failed Devices : 0
Spare Devices : 0
Chunk Size : 512K
Consistency Policy : none
Name : homeserver:127 (local to host homeserver)
UUID : c1e68c25:0cdaa7e9:3d0a14a0:5717a5f1
Events : 0
Number Major Minor RaidDevice State
0 8 177 0 active sync /dev/sdl1
1 8 161 1 active sync /dev/sdk1
2 8 193 2 active sync /dev/sdm1
Time to start the backup!
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