View Full Version : [ubuntu] Migrate Ubuntu Mdadm RAID6 array from Feisty (07.10) to latest. Possible?

February 3rd, 2018, 12:37 AM
My ancient Ubuntu installation has been out of service for several years now. I was running a RAID 6 array on it using the built-in mdadm up until the boot drive died. The individual RAID disks are still intact as is the RAID blocks that can re-create the array. I have backups of the configs somewhere so that will help also if I can rebuild. Below is the Linux kernel and mdadm I was using:

Linux version 2.6.35-25-server (buildd@crested) (gcc version 4.4.5 (Ubuntu/Linaro 4.4.4-14ubuntu5) ) #44-Ubuntu SMP Fri Jan 21 19:09:14 UTC 2011 (Ubuntu 2.6.35-25.44-server

root@mythbe:/var/log# mdadm --detail /dev/md0
Version : 0.90
Creation Time : Mon Sep 15 23:51:21 2008
Raid Level : raid6
Array Size : 1953535744 (1863.04 GiB 2000.42 GB)
Used Dev Size : 488383936 (465.76 GiB 500.11 GB)
Raid Devices : 6
Total Devices : 5
Preferred Minor : 0
Persistence : Superblock is persistent

Update Time : Fri Nov 26 13:49:22 2010
State : clean, degraded
Active Devices : 5
Working Devices : 5
Failed Devices : 0
Spare Devices : 0

Layout : left-symmetric
Chunk Size : 64K

UUID : 614a41ae:61369299:f04c99b8:3fd94616 (local to host mythbe)
Events : 0.178464

Number Major Minor RaidDevice State
0 8 1 0 active sync /dev/sda1
1 8 17 1 active sync /dev/sdb1
2 8 49 2 active sync /dev/sdd1
3 0 0 3 removed
4 8 97 4 active sync /dev/sdg1
5 8 81 5 active sync /dev/sdf1

I am in the process of upgrading the computer with newer hardware and installing the latest Ubuntu. I'm wondering if I can recover the array on the new installation if I import the disks to the machine after the OS install? Or has the Ubuntu distribution and mdadm moved on so far that this would be an impossible task?

(p.s. I have backups)

February 3rd, 2018, 05:05 AM
If you've got backups it wouldn't hurt to try. Be prepared for it not to work though. I'm curious if something that old can work with the latest and greatest.

February 4th, 2018, 11:54 PM
UPDATE: Bottom-line is that mdadm works on an array built using a very old Ubuntu.

I upgraded the hardware in the computer and then installed Ubuntu Server 16.04 LTS on a USB disk. Booted the new OS and all the RAID elements were visible. I updated the /etc/mdadm/mdadm.conf manually from the information I saved and (after some head scratching) issued the command mdadm --assemble --scan --force -v. The array was detected by mdmadm as being dirty and so the system started to rebuild it. When finished, the volume wouldn't mount until I did a fsck.