mdadm Linux Software RAID QuickStart Guide

Create New RAID 1 Array:

First setup your partitions (make sure they are exactly the same size)
In my example I have sda3 and sdb3 which are 500GB in size.

mdadm --create /dev/md2 --level=1 --raid-devices=2 /dev/sda3 /dev/sdb3
mdadm: array /dev/md2 started.

Check Status Of The Array

*Note I already have other arrays md0 and md1.

You can see below that md2 is syncing at a speed of about 91MB per sec.

cat /proc/mdstat

Personalities : [raid1]
md2 : active raid1 sdb3[1] sda3[0]
488287552 blocks [2/2] [UU]
[>....................] resync = 0.5% (2460992/488287552) finish=88.8min speed=91147K/sec

md1 : active raid1 sda2[0] sdb2[1]
29302464 blocks [2/2] [UU]

md0 : active raid1 sdb1[1] sda1[0]
58604992 blocks [2/2] [UU]

unused devices:

Check the basic details of an array:

mdadm /dev/md0
/dev/md0: 55.89GiB raid1 2 devices, 0 spares. Use mdadm --detail for more detail.
/dev/md0: No md super block found, not an md component.

More Detail

mdadm --detail /dev/md0

Version : 0.90
Creation Time : Tue Aug 31 22:37:52 2010
Raid Level : raid1
Array Size : 58604992 (55.89 GiB 60.01 GB)
Used Dev Size : 58604992 (55.89 GiB 60.01 GB)
Raid Devices : 2
Total Devices : 2
Preferred Minor : 0
Persistence : Superblock is persistent

Update Time : Wed Sep 1 18:39:53 2010
State : active
Active Devices : 2
Working Devices : 2
Failed Devices : 0
Spare Devices : 0

UUID : 7b4e9a42:823c7ee5:0d6ee1b8:30df68a8
Events : 0.7

Number Major Minor RaidDevice State
0 8 1 0 active sync /dev/sda1
1 8 17 1 active sync /dev/sdb1

Update /etc/mdadm.conf File

mdadm --brief --detail /dev/md0

ARRAY /dev/md0 level=raid1 num-devices=2 metadata=0.90 UUID=7b4e9a42:823c7ee5:0d6ee1b8:30df68a8

To edit the /etc/mdadm.conf file directly just run the command like this make sure to use the ">>" or you will wipe out any existing array info.

mdadm --brief --detail /dev/md0 >> /etc/mdadm.conf


mdadm, linux, software, raid, quickstart, array, partitions, sda, sdb, gb, dev, md, devices, arrays, syncing, mb, proc, mdstat, personalities, active, uu, resync, min, unused, gib, spares, component, creation, tue, aug, preferred, persistence, superblock, persistent, update, wed, sep, uuid, ee, df, raiddevice, sync, etc, conf, num, metadata, edit, quot, existing, info,

Latest Articles

  • ImageMagick Convert PDF Not Authorized
  • ImageMagick Converted PDF to JPEG some files have a black background solution
  • Linux Mint Mate Customize the Lock screen messages and hide username and real name
  • Ubuntu/Gnome/Mint/Centos How To Take a partial screenshot
  • ssh how to verify your host key / avoid MIM attacks
  • Cisco IP Phone CP-8845 8800/8900 Series How To Reset To Factory Settings Instructions
  • ls how to list ONLY directories
  • How to encrypt your SSH private key file id_rsa
  • Linux Mint 18 Disable User Name List from showing on Login Screen
  • Firefox Cannot Hit Enter Key In Address Bar and Location History Not Working
  • Cisco Unified Communications Manager / CUCM IP 8.6,10,12 Install Error Solution
  • Ubuntu Debian Mint Linux SSHD OpenSSH Server Not Starting After Reboot Solution
  • nmap how to scan for all ports and not just the 1000 most common ports
  • Windows 7,8,10 and Server 2008, 2012, 2016, 2019 Read Only Attribute Won't Go Away
  • bind / named how to make a wildcard record and retain defined A records
  • Cisco Unified Communications Manager 12 Install Errors on Proxmox/KVM
  • Local Vs Universally Administered MAC Address NIC Refuses to come up
  • Cisco Unified Communications Manager 12 CUCM 12 - How To Enable Video Calling
  • Windows 7, 8, 10, Windows Server 2008, 2012, 2016, 2019 How To AC97 Audio Drivers and Other Unsigned Drivers
  • Cisco Unified Communications Manager / CUCM IP Telephony Definitions