I've recently added a 5th drive to my software raid array -- and mdadm has accepted it:
$ lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
nvme0n1 259:0 0 894.3G 0 disk
├─nvme0n1p1 259:4 0 512M 0 part
│ └─md0 9:0 0 511M 0 raid1 /boot
└─nvme0n1p2 259:5 0 893.8G 0 part
└─md1 9:1 0 3.5T 0 raid5
├─vg0-swap 253:0 0 32G 0 lvm [SWAP]
├─vg0-tmp 253:1 0 50G 0 lvm /tmp
└─vg0-root 253:2 0 2.6T 0 lvm /
nvme3n1 259:1 0 894.3G 0 disk
├─nvme3n1p1 259:6 0 512M 0 part
│ └─md0 9:0 0 511M 0 raid1 /boot
└─nvme3n1p2 259:7 0 893.8G 0 part
└─md1 9:1 0 3.5T 0 raid5
├─vg0-swap 253:0 0 32G 0 lvm [SWAP]
├─vg0-tmp 253:1 0 50G 0 lvm /tmp
└─vg0-root 253:2 0 2.6T 0 lvm /
nvme2n1 259:2 0 894.3G 0 disk
├─nvme2n1p1 259:8 0 512M 0 part
│ └─md0 9:0 0 511M 0 raid1 /boot
└─nvme2n1p2 259:9 0 893.8G 0 part
└─md1 9:1 0 3.5T 0 raid5
├─vg0-swap 253:0 0 32G 0 lvm [SWAP]
├─vg0-tmp 253:1 0 50G 0 lvm /tmp
└─vg0-root 253:2 0 2.6T 0 lvm /
nvme1n1 259:3 0 894.3G 0 disk
├─nvme1n1p1 259:10 0 512M 0 part
│ └─md0 9:0 0 511M 0 raid1 /boot
└─nvme1n1p2 259:11 0 893.8G 0 part
└─md1 9:1 0 3.5T 0 raid5
├─vg0-swap 253:0 0 32G 0 lvm [SWAP]
├─vg0-tmp 253:1 0 50G 0 lvm /tmp
└─vg0-root 253:2 0 2.6T 0 lvm /
nvme4n1 259:12 0 894.3G 0 disk
├─nvme4n1p1 259:15 0 512M 0 part
│ └─md0 9:0 0 511M 0 raid1 /boot
└─nvme4n1p2 259:16 0 893.8G 0 part
└─md1 9:1 0 3.5T 0 raid5
├─vg0-swap 253:0 0 32G 0 lvm [SWAP]
├─vg0-tmp 253:1 0 50G 0 lvm /tmp
└─vg0-root 253:2 0 2.6T 0 lvm /
$ cat /proc/mdstat
Personalities : [raid1] [raid6] [raid5] [raid4] [linear] [multipath] [raid0] [raid10]
md0 : active raid1 nvme4n1p1[4] nvme1n1p1[2] nvme3n1p1[0] nvme0n1p1[3] nvme2n1p1[1]
523264 blocks super 1.2 [5/5] [UUUUU]
md1 : active raid5 nvme4n1p2[5] nvme2n1p2[1] nvme1n1p2[2] nvme3n1p2[0] nvme0n1p2[4]
3748134912 blocks super 1.2 level 5, 512k chunk, algorithm 2 [5/5] [UUUUU]
bitmap: 3/7 pages [12KB], 65536KB chunk
unused devices: <none>
The issue is that my filesystem still thinks that I only have 4 drives attached and hasn't grown to take advantage of the extra drive.
I've tried
$ sudo e2fsck -fn /dev/md1
e2fsck 1.45.5 (07-Jan-2020)
Warning! /dev/md1 is in use.
ext2fs_open2: Bad magic number in super-block
e2fsck: Superblock invalid, trying backup blocks...
e2fsck: Bad magic number in super-block while trying to open /dev/md1
The superblock could not be read or does not describe a valid ext2/ext3/ext4
filesystem. If the device is valid and it really contains an ext2/ext3/ext4
filesystem (and not swap or ufs or something else), then the superblock
is corrupt, and you might try running e2fsck with an alternate superblock:
e2fsck -b 8193 <device>
or
e2fsck -b 32768 <device>
/dev/md1 contains a LVM2_member file system
and
$ sudo resize2fs /dev/md1
resize2fs 1.45.5 (07-Jan-2020)
resize2fs: Device or resource busy while trying to open /dev/md1
Couldn't find valid filesystem superblock.
But so far no luck:
$ df
Filesystem 1K-blocks Used Available Use% Mounted on
udev 131841212 0 131841212 0% /dev
tmpfs 26374512 2328 26372184 1% /run
/dev/mapper/vg0-root 2681290296 2329377184 215641036 92% /
tmpfs 131872540 0 131872540 0% /dev/shm
tmpfs 5120 0 5120 0% /run/lock
tmpfs 131872540 0 131872540 0% /sys/fs/cgroup
/dev/md0 498532 86231 386138 19% /boot
/dev/mapper/vg0-tmp 52427196 713248 51713948 2% /tmp
tmpfs 26374508 0 26374508 0% /run/user/1001
tmpfs 26374508 0 26374508 0% /run/user/1002
I hope this is enough info - but happy to provide more if it is useful.
