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 -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html