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Configure software RAID on Linux using MDADM - Do it now
This article covers how to Configure software RAID on Linux using MDADM.
To Install a Software Raid Management Tool:
To install mdadm, run the installation command:
1. For CentOS/Red Hat (yum/dnf is used): $ yum install mdadm
2. For Ubuntu/Debian: $ apt-get install mdadm
3. SUSE: $ sudo zypper install mdadm
4. Arch Linux: $ sudo pacman -S mdadm
Terms related to Integrity of a RAID Array:
1. Version – the metadata version
2. Creation Time – the date and time of RAID creation
3. Raid Level – the level of a RAID array
4. Array Size – the size of the RAID disk space
5. Used Dev Size – the space size used by devices
6. Raid Device – the number of disks in the RAID
7. Total Devices – is the number of disks added to the RAID
8. State – is the current state (clean — it is OK)
9. Active Devices – number of active disks in the RAID
10. Working Devises – number of working disks in the RAID
11. Failed Devices – number of failed devices in the RAID
12. Spare Devices – number of spare disks in the RAID
13. Consistency Policy – is the parameter that sets the synchronization type after a failure, rsync is a full synchronization after RAID array recovery (bitmap, journal, ppl modes are available)
14. UUID – raid array identifier
To Recovering from a Disk Failure in RAID, Disk Replacement:
If one of the disks in a RAID failed or damaged, you may replace it with another one. First of all, find out if the disc is damaged and needs to be replaced.
# cat /proc/mdstat
To Add or Remove Disks to Software RAID on Linux:
1. If you need to remove the previously created mdadm RAID device, unmount it:
# umount /backup
2. Then run this command:
# mdadm -S /dev/md0
mdadm: stopped /dev/md0
3. After destroying the RAID array, it won’t detected as a separate disk device:
# mdadm -S /dev/md0
mdadm: error opening /dev/md0: No such file or directory
4. You can scan all connected drives and re-create a previously removed (failed) RAID device according to the metadata on physical drives. Run the following command:
# mdadm --assemble —scan
About Mdmonitor: RAID State Monitoring & Email Notifications:
The mdmonitor daemon can be used to monitor the status of the RAID.
1. First, you must create the /etc/mdadm.conf file containing the current array configuration:
# mdadm –detail –scan > /etc/mdadm.conf
The mdadm.conf file is not created automatically. You must create and update it manually.
2. Add to the end of /etc/mdadm.conf the administrator email address to which you want to send notifications in case of any RAID problems:
MAILADDR raidadmin@woshub.com
3. Then restart mdmonitor service using systemctl:
# systemctl restart mdmonitor
Then the system will notify you by e-mail if there are any mdadm errors or faulty disks.
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