Raid 10 Issue

[Stefan Lamby <webmaster@peter-speer.de>]

Hello List.

I was setting up a new machine using ubuntu 14.04.02 lts using its installer,
configuring a raid 10 with 2 disks and lvm on top of it. I was using 2 disks and
now I like to add 2 more disks to the array so i want to end up with 4 disks, no
spare.

Searching the internet I found that I am not able to --grow the array with the
mdadm version this ubuntu is using (v3.2.5).
Is that right?

So I decided to build a new array that way and try to move my data afterwards,
which failed:
(Is it OK to do it that way or do you recommend another?)

root@kvm15:~# mdadm --verbose --create --level=10 --raid-devices=4 /dev/md10
missing missing /dev/sdc1 /dev/sdd1
mdadm: layout defaults to n2
mdadm: layout defaults to n2
mdadm: chunk size defaults to 512K
mdadm: /dev/sdc1 appears to be part of a raid array:
    level=raid10 devices=4 ctime=Fri Feb 27 15:49:14 2015
mdadm: /dev/sdd1 appears to be part of a raid array:
    level=raid10 devices=4 ctime=Fri Feb 27 15:49:14 2015
mdadm: size set to 1904165376K
Continue creating array? y
mdadm: Defaulting to version 1.2 metadata
mdadm: RUN_ARRAY failed: Input/output error
              <<<<<<<<<<<<<<<<<<<<<<<<<<<
root@kvm15:~# 
root@kvm15:~# 
root@kvm15:~# cat /proc/mdstat 
Personalities : [linear] [multipath] [raid0] [raid1] [raid10] [raid6] [raid5]
[raid4] 
md0 : active raid10 sdb1[1] sda1[0]
      1904165376 blocks super 1.2 2 near-copies [2/2] [UU]
      
unused devices: <none>


md0 btw. is the current (running) array.

I did a few tries to get this running. This is must be the reason why mdadm
detects already existing raid config.

The partitions for sdc and sdd are created using fdisk, they do have the same
layout like disk sdb, which looks like this:

(parted) print                                                            
Modell: ATA WDC WD20PURX-64P (scsi)
Festplatte  /dev/sdc:  2000GB
Sektorgröße (logisch/physisch): 512B/4096B
Partitionstabelle: msdos

Nummer  Anfang  Ende    Größe   Typ      Dateisystem  Flags
 1      50.4GB  2000GB  1950GB  primary               RAID


Any help is very welcome.

Thanks.
Stefan
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