I have an Ubuntu 18.04 server with two 1Tb drives in a software RAID1 array, configured during the OS installation process. I wanted the check the health of the array and disks this evening and am not sure if there is a problem with one of my drives.
I see in the 'mdadm --detail /dev/md0' output that one of the drives appears to be removed, and I see from another askubuntu question that the [_U] in the 'cat /proc/mdstat' command output is possibly a signal that a partition has failed.
From the results below, has a drive failed? If so, what is the best course of action? Also, how do I set it so it emails me when a drive fails?
sudo fdisk -l
Disk /dev/loop0: 99.2 MiB, 104030208 bytes, 203184 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 /dev/loop2: 99.2 MiB, 104026112 bytes, 203176 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 /dev/sda: 931.5 GiB, 1000204886016 bytes, 1953525168 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: gpt
Disk identifier: 310AB5A9-6622-49D9-82C3-B1F2E53DD560
Device Start End Sectors Size Type
/dev/sda1 2048 2099199 2097152 1G Linux filesystem
/dev/sda2 2099200 1953521663 1951422464 930.5G Linux filesystem
Disk /dev/sdb: 931.5 GiB, 1000204886016 bytes, 1953525168 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: gpt
Disk identifier: D634E279-44CC-4ED5-B380-07D02C3C3601
Device Start End Sectors Size Type
/dev/sdb1 2048 4095 2048 1M BIOS boot
/dev/sdb2 4096 2101247 2097152 1G Linux filesystem
/dev/sdb3 2101248 1953521663 1951420416 930.5G Linux filesystem
Disk /dev/md0: 930.4 GiB, 998991986688 bytes, 1951156224 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
loop0 7:0 0 99.2M 1 loop /snap/core/10908
loop2 7:2 0 99.2M 1 loop /snap/core/10859
sda 8:0 0 931.5G 0 disk
├─sda1 8:1 0 1G 0 part
└─sda2 8:2 0 930.5G 0 part
sdb 8:16 0 931.5G 0 disk
├─sdb1 8:17 0 1M 0 part
├─sdb2 8:18 0 1G 0 part /boot
└─sdb3 8:19 0 930.5G 0 part
└─md0 9:0 0 930.4G 0 raid1 /
cat /etc/mdadm/mdadm.conf
ARRAY /dev/md0 metadata=1.2 name=ubuntu-server:0 UUID=1d9d79bd:d675f751:144db975:0d24caa9
MAILADDR root
sudo mdadm --detail /dev/md0
/dev/md0:
Version : 1.2
Creation Time : Fri Aug 30 21:55:50 2019
Raid Level : raid1
Array Size : 975578112 (930.38 GiB 998.99 GB)
Used Dev Size : 975578112 (930.38 GiB 998.99 GB)
Raid Devices : 2
Total Devices : 1
Persistence : Superblock is persistent
Intent Bitmap : Internal
Update Time : Sat Apr 3 23:18:52 2021
State : clean, degraded
Active Devices : 1
Working Devices : 1
Failed Devices : 0
Spare Devices : 0
Consistency Policy : bitmap
Name : ubuntu-server:0
UUID : 1d9d79bd:d675f751:144db975:0d24caa9
Events : 1907228
Number Major Minor RaidDevice State
- 0 0 0 removed
1 8 19 1 active sync /dev/sdb3
cat /proc/mdstat
Personalities : [raid1] [linear] [multipath] [raid0] [raid6] [raid5] [raid4] [raid10]
md0 : active raid1 sdb3[1]
975578112 blocks super 1.2 [2/1] [_U]
bitmap: 8/8 pages [32KB], 65536KB chunk
unused devices: <none>
mdadm --manage /dev/md0 --add /dev/sda2but I am not 100% about that since I did not set up your system but the closest guess I can see with that partition being the closest to sdb3.sudo smartctl -a /dev/sda | grep overallto show you if the drive PASSED or FAILED.