mdadm – v3.2.5 – 18th May 2012
Currently have:
Version : 1.2
Creation Time : Tue Jun 25 19:03:31 2013
Raid Level : raid5
Array Size : 2930135040 (2794.39 GiB 3000.46 GB)
Used Dev Size : 2930135040 (2794.39 GiB 3000.46 GB)
Raid Devices : 2
Total Devices : 2
Persistence : Superblock is persistent
Update Time : Wed Jun 26 17:17:01 2013
State : clean
Active Devices : 2
Working Devices : 2
Failed Devices : 0
Spare Devices : 0
Layout : left-symmetric
Chunk Size : 512K
Name : desktop:0 (local to host desktop)
UUID : 91a6c44d:21226975:8d2dc41a:7fcff414
Events : 7434
Number Major Minor RaidDevice State
2 8 16 0 active sync /dev/sdb
1 8 48 1 active sync /dev/sdd
Problem:
/dev/sdc is full of data.
I want to grow the raid to 3 devices in degraded state (therefore 6TB), copy all the data to the raid. Then actually add /dev/sdc.
Already tried:
andey@desktop:~$ sudo mdadm --add /dev/md127 missing
mdadm: 'missing' only meaningful with --re-add
andey@desktop:~$ sudo mdadm --re-add /dev/md127 missing
No complaints from mdadm, however when I checked the RAID there wasn't a third drive
andey@desktop:~$ sudo mdadm --grow /dev/md127 --raid-devices=3
mdadm: Need 1 spare to avoid degraded array, and only have 0.
Use --force to over-ride this check.
andey@desktop:~$ sudo mdadm --grow /dev/md127 --raid-devices=3 --force
mdadm: Need to backup 1024K of critical section..
mdadm: /dev/md127: Cannot grow - need a spare or backup-file to backup critical section
Best Answer
You are almost there. Now use the --backup-file option to specify a temp file for mdadm to use. Do not put it on your md array.