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

Participate now!

Don’t have an account yet? Register yourself now and be a part of our community!