Remove third hard disk from RAID 1

    • OMV 2.x
    • Remove third hard disk from RAID 1

      Hi all,

      I created a RAID 1 with 2 disks, but I expected that the second one is at the end of it's lifetime, so I wanted to replace it with an other one. So far, so good.
      However, I wanted to do this only with the GUI, and because I saw no "remove", I thought I will add the new one first, then after sync I will remove the old one. (I know, I will read the manuals first...)
      But when I removed the old one, the raid became "clean, degraded", with two hard disks. How can I make it clean again?

      details of the raid:
      Version : 1.2
      Creation Time : Thu Oct 20 00:02:50 2016
      Raid Level : raid1
      Array Size : 488222528 (465.61 GiB 499.94 GB)
      Used Dev Size : 488222528 (465.61 GiB 499.94 GB)
      Raid Devices : 3
      Total Devices : 2
      Persistence : Superblock is persistent

      Update Time : Sun Oct 23 17:41:34 2016
      State : clean, degraded
      Active Devices : 2
      Working Devices : 2
      Failed Devices : 0
      Spare Devices : 0

      Name : raspberrypi:NAS (local to host raspberrypi)
      UUID : 1b5d2b14:93f00308:227f0e76:04eb9d3d
      Events : 503

      Number Major Minor RaidDevice State
      0 0 0 0 removed
      1 8 16 1 active sync /dev/sdb
      2 8 0 2 active sync /dev/sda

      And the rest that is required by the sticky forum

      output of cat /proc/mdstat:
      Personalities : [raid1]
      md0 : active raid1 sdb[1] sda[2]
      488222528 blocks super 1.2 [3/2] [_UU]

      output of blkid:
      /dev/mmcblk0p1: SEC_TYPE="msdos" LABEL="boot" UUID="7D5C-A285" TYPE="vfat"
      /dev/mmcblk0p2: UUID="5d18be51-3217-4679-9c72-a54e0fc53d6b" TYPE="ext4" LABEL="omv"
      /dev/mmcblk0p3: LABEL="data" UUID="fa36508a-b3c4-4499-b30a-711dd5994225" TYPE="ext4"
      /dev/sdb: UUID="1b5d2b14-93f0-0308-227f-0e7604eb9d3d" UUID_SUB="26052ce7-837f-e2c0-2471-ff05bff5cb74" LABEL="raspberrypi:NAS" TYPE="linux_raid_member"
      /dev/md0: LABEL="nas" UUID="d23f4887-0b6e-4dc0-899d-96f5795f1d1f" TYPE="ext4"
      /dev/sda: UUID="1b5d2b14-93f0-0308-227f-0e7604eb9d3d" UUID_SUB="2a92f891-d186-59fa-d764-0eec290c2104" LABEL="raspberrypi:NAS" TYPE="linux_raid_member"

      output of fdisk -l:
      Disk /dev/mmcblk0: 7948 MB, 7948206080 bytes
      4 heads, 16 sectors/track, 242560 cylinders, total 15523840 sectors
      Units = sectors of 1 * 512 = 512 bytes
      Sector size (logical/physical): 512 bytes / 512 bytes
      I/O size (minimum/optimal): 512 bytes / 512 bytes
      Disk identifier: 0x000b5098

      Device Boot Start End Blocks Id System
      /dev/mmcblk0p1 8192 122879 57344 c W95 FAT32 (LBA)
      /dev/mmcblk0p2 122880 7028735 3452928 83 Linux
      /dev/mmcblk0p3 7028736 15523839 4247552 83 Linux

      Disk /dev/sda: 500.1 GB, 500107862016 bytes
      255 heads, 63 sectors/track, 60801 cylinders, total 976773168 sectors
      Units = sectors of 1 * 512 = 512 bytes
      Sector size (logical/physical): 512 bytes / 512 bytes
      I/O size (minimum/optimal): 512 bytes / 512 bytes
      Disk identifier: 0x00000000

      Disk /dev/sda doesn't contain a valid partition table

      Disk /dev/sdb: 500.1 GB, 500074283008 bytes
      255 heads, 63 sectors/track, 60797 cylinders, total 976707584 sectors
      Units = sectors of 1 * 512 = 512 bytes
      Sector size (logical/physical): 512 bytes / 512 bytes
      I/O size (minimum/optimal): 512 bytes / 512 bytes
      Disk identifier: 0x00000000

      Disk /dev/sdb doesn't contain a valid partition table

      Disk /dev/md0: 499.9 GB, 499939868672 bytes
      2 heads, 4 sectors/track, 122055632 cylinders, total 976445056 sectors
      Units = sectors of 1 * 512 = 512 bytes
      Sector size (logical/physical): 512 bytes / 512 bytes
      I/O size (minimum/optimal): 512 bytes / 512 bytes
      Disk identifier: 0x00000000

      Disk /dev/md0 doesn't contain a valid partition table

      contents of conf:
      # mdadm.conf
      #
      # Please refer to mdadm.conf(5) for information about this file.
      #

      # by default, scan all partitions (/proc/partitions) for MD superblocks.
      # alternatively, specify devices to scan, using wildcards if desired.
      # Note, if no DEVICE line is present, then "DEVICE partitions" is assumed.
      # To avoid the auto-assembly of RAID devices a pattern that CAN'T match is
      # used if no RAID devices are configured.
      DEVICE partitions

      # auto-create devices with Debian standard permissions
      CREATE owner=root group=disk mode=0660 auto=yes

      # automatically tag new arrays as belonging to the local system
      HOMEHOST <system>

      # definitions of existing MD arrays
      ARRAY /dev/md0 metadata=1.2 spares=1 name=raspberrypi:NAS UUID=1b5d2b14:93f00308:227f0e76:04eb9d3d

      output of mdadm:
      ARRAY /dev/md0 level=raid1 num-devices=3 metadata=1.2 name=raspberrypi:NAS UUID=1b5d2b14:93f00308:227f0e76:04eb9d3d
      devices=/dev/sdb,/dev/sda