Linux/mdadm - Revision history

Kenneth: /* Change Drive Name */

2025-09-08T20:14:03Z

Change Drive Name

← Older revision		Revision as of 20:14, 8 September 2025
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	Change the name with: (to /dev/md1) <ref>https://superuser.com/questions/346719/how-to-change-the-name-of-an-md-device-mdadm</ref>		Change the name with: (to /dev/md1) <ref>https://superuser.com/questions/346719/how-to-change-the-name-of-an-md-device-mdadm</ref>
	mdadm -A --update=name --name=1 /dev/md1 /dev/nvme0n1p1 /dev/nvme1n1p1 /dev/nvme2n1p1 /dev/nvme3n1p1		mdadm -A --update=name --name=1 /dev/md1 /dev/nvme0n1p1 /dev/nvme1n1p1 /dev/nvme2n1p1 /dev/nvme3n1p1

			If the "name" number collides with another array, it will pick some high number like /dev/md127

	=== Stop array ===		=== Stop array ===

Kenneth: /* Create /etc/mdadm.conf */

2025-09-08T20:12:30Z

Create /etc/mdadm.conf

← Older revision		Revision as of 20:12, 8 September 2025
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	# Ubuntu 24		# Ubuntu 24
	mdadm --detail --scan --verbose >> /etc/mdadm/mdadm.conf		mdadm --detail --scan --verbose >> /etc/mdadm/mdadm.conf
			mdadm -Dsv >> /etc/mdadm/mdadm.conf

	# make 24 universal with ubuntu 20 below:		# make 24 universal with ubuntu 20 below:
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	# sudo mdadm -A /dev/md0 # --assemble		# sudo mdadm -A /dev/md0 # --assemble
	# sudo mdadm -A md0 # --assemble		# sudo mdadm -A md0 # --assemble

			=== Change Drive Name ===

			/dev/mdX usually created based on drive "name" number (eg. myserver:2 will create /dev/md2)

			Change the name with: (to /dev/md1) <ref>https://superuser.com/questions/346719/how-to-change-the-name-of-an-md-device-mdadm</ref>
			mdadm -A --update=name --name=1 /dev/md1 /dev/nvme0n1p1 /dev/nvme1n1p1 /dev/nvme2n1p1 /dev/nvme3n1p1

	=== Stop array ===		=== Stop array ===

Kenneth: /* Commands */

2025-09-08T20:08:39Z

Commands

← Older revision		Revision as of 20:08, 8 September 2025
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	== Commands ==		== Commands ==

	Show all md devices status:		=== Show all md devices status ===
	cat /proc/mdstat		cat /proc/mdstat

	Show md device details: (needs full path)		=== Show md device details ===
			(needs full path)
	mdadm --detail /dev/md0		mdadm --detail /dev/md0
	mdadm -D /dev/md/thebig		mdadm -D /dev/md/thebig

	Create RAID 0 (stripe):		=== Create RAID 0 (stripe) ===
	mdadm --create --verbose /dev/md0 --level=raid0 --raid-devices=3 /dev/hd[cde]1		mdadm --create --verbose /dev/md0 --level=raid0 --raid-devices=3 /dev/hd[cde]1

	Create RAID 1 (mirror):		=== Create RAID 1 (mirror) ===
	mdadm --create --verbose /dev/md0 --level=raid1 --raid-devices=2 --spare-devices=0 /dev/hd[bc]1		mdadm --create --verbose /dev/md0 --level=raid1 --raid-devices=2 --spare-devices=0 /dev/hd[bc]1
	mdadm --create --verbose /dev/md0 --level=raid1 --raid-devices=2 --spare-devices=1 /dev/hd[bce]1		mdadm --create --verbose /dev/md0 --level=raid1 --raid-devices=2 --spare-devices=1 /dev/hd[bce]1

	Create RAID 5 (stripe with parity):		=== Create RAID 5 (stripe with parity) ===
	mdadm --create --verbose /dev/md0 --level=5 --raid-devices=3 --spare-devices=0 /dev/sd[bcd]1		mdadm --create --verbose /dev/md0 --level=5 --raid-devices=3 --spare-devices=0 /dev/sd[bcd]1
	mdadm --create --verbose /dev/md0 --level=5 --raid-devices=3 --spare-devices=1 /dev/sd[bcde]1		mdadm --create --verbose /dev/md0 --level=5 --raid-devices=3 --spare-devices=1 /dev/sd[bcde]1

	Create RAID 10: (striped mirrors)		=== Create RAID 10 (striped mirrors) ===
	mdadm --create --verbose /dev/md0 --level=10 --raid-devices=4 --spare-devices=0 /dev/sd[bcde]1		mdadm --create --verbose /dev/md0 --level=10 --raid-devices=4 --spare-devices=0 /dev/sd[bcde]1
	mdadm --create --verbose /dev/md0 --level=10 --raid-devices=4 --spare-devices=1 /dev/sd[bcdef]1		mdadm --create --verbose /dev/md0 --level=10 --raid-devices=4 --spare-devices=1 /dev/sd[bcdef]1
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	# Can be created with an odd number of disks (e.g., 3, 5, etc.), which is not possible in traditional RAID10.		# Can be created with an odd number of disks (e.g., 3, 5, etc.), which is not possible in traditional RAID10.

	Add partition to md device:		=== Add partition to md device ===
	# mdadm /dev/md0 --add /dev/sdb1		# mdadm /dev/md0 --add /dev/sdb1
	mdadm md0 --add /dev/sdb1		mdadm md0 --add /dev/sdb1

	Fail and remove partition of md device:		=== Fail and remove partition of md device ===
	# mdadm /dev/md0 --fail /dev/sdb1		# mdadm /dev/md0 --fail /dev/sdb1
	# mdadm /dev/md0 --remove /dev/sdb1		# mdadm /dev/md0 --remove /dev/sdb1
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	mdadm md0 --remove /dev/sdb1		mdadm md0 --remove /dev/sdb1

	Start drive without resync:		=== Start drive without resync ===
	# mdadm -S /dev/md0 # --stop		# mdadm -S /dev/md0 # --stop
	# mdadm -A --assume-clean /dev/md0 # --assemble		# mdadm -A --assume-clean /dev/md0 # --assemble
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	mdadm -A --assume-clean md0 # --assemble		mdadm -A --assume-clean md0 # --assemble

	Create /etc/mdadm.conf (high to low detail, any will work) [https://serverfault.com/questions/170817/software-mdadm-raid-5-inactive-md0-showing]		=== Create /etc/mdadm.conf ===

			(high to low detail, any will work) [https://serverfault.com/questions/170817/software-mdadm-raid-5-inactive-md0-showing]
	# Ubuntu 24		# Ubuntu 24
	mdadm --detail --scan --verbose >> /etc/mdadm/mdadm.conf		mdadm --detail --scan --verbose >> /etc/mdadm/mdadm.conf
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	# sudo mdadm -A md0 # --assemble		# sudo mdadm -A md0 # --assemble

	Stop array:		=== Stop array ===
	# mdadm --stop /dev/md0		# mdadm --stop /dev/md0
	mdadm --stop md0		mdadm --stop md0
	mdadm -S /dev/md/thebig		mdadm -S /dev/md/thebig

	Start (assemble) array:		=== Start (assemble) array ===
	# mdadm --assemble /dev/md0		# mdadm --assemble /dev/md0
	mdadm --verbose --assemble md0		mdadm --verbose --assemble md0
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	mdadm -v -A thebig		mdadm -v -A thebig

	Add disk to RAID 5:		=== Add disk to RAID 5 ===
	unmount /dev/md1		unmount /dev/md1
	mdadm --add /dev/md1 /dev/sdb3		mdadm --add /dev/md1 /dev/sdb3
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	resize2fs /dev/md3		resize2fs /dev/md3

	fdisk to 'Linux raid':		=== fdisk to 'Linux raid' ===
	type 'fd'		type 'fd'

Kenneth: /* Commands */

2025-09-08T17:31:37Z

Commands

← Older revision		Revision as of 17:31, 8 September 2025
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	# So it's striped mirrors, technically: each stripe is made of mirrored disks.		# So it's striped mirrors, technically: each stripe is made of mirrored disks.
	# This is different from some hardware RAID implementations where RAID10 is built as a mirror of stripes (mirrored stripe), meaning two RAID0 arrays are mirrored.		# This is different from some hardware RAID implementations where RAID10 is built as a mirror of stripes (mirrored stripe), meaning two RAID0 arrays are mirrored.
			# Offers redundancy and performance.
			# Can be created with an odd number of disks (e.g., 3, 5, etc.), which is not possible in traditional RAID10.

	Add partition to md device:		Add partition to md device:

Kenneth: /* Commands */

2025-09-08T17:30:52Z

Commands

← Older revision		Revision as of 17:30, 8 September 2025
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	mdadm --create --verbose /dev/md0 --level=5 --raid-devices=3 --spare-devices=1 /dev/sd[bcde]1		mdadm --create --verbose /dev/md0 --level=5 --raid-devices=3 --spare-devices=1 /dev/sd[bcde]1

	Create RAID 10: (~~mirrored stripe~~)		Create RAID 10: (striped mirrors)
	mdadm --create --verbose /dev/md0 --level=10 --raid-devices=4 --spare-devices=0 /dev/sd[bcde]1		mdadm --create --verbose /dev/md0 --level=10 --raid-devices=4 --spare-devices=0 /dev/sd[bcde]1
	mdadm --create --verbose /dev/md0 --level=10 --raid-devices=4 --spare-devices=1 /dev/sd[bcdef]1		mdadm --create --verbose /dev/md0 --level=10 --raid-devices=4 --spare-devices=1 /dev/sd[bcdef]1

			# RAID10 in mdadm is built using RAID1 pairs (mirrors), then striped across those pairs.
			# So it's striped mirrors, technically: each stripe is made of mirrored disks.
			# This is different from some hardware RAID implementations where RAID10 is built as a mirror of stripes (mirrored stripe), meaning two RAID0 arrays are mirrored.

	Add partition to md device:		Add partition to md device:

Kenneth: /* Commands */

2025-09-08T17:28:39Z

Commands

← Older revision		Revision as of 17:28, 8 September 2025
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	Create RAID 0 (stripe):		Create RAID 0 (stripe):
	mdadm --create --verbose /dev/md0 --level=raid0 --raid-devices=3 /dev/hd[cde]1		mdadm --create --verbose /dev/md0 --level=raid0 --raid-devices=3 /dev/hd[cde]1

			Create RAID 1 (mirror):
			mdadm --create --verbose /dev/md0 --level=raid1 --raid-devices=2 --spare-devices=0 /dev/hd[bc]1
			mdadm --create --verbose /dev/md0 --level=raid1 --raid-devices=2 --spare-devices=1 /dev/hd[bce]1

	Create RAID 5 (stripe with parity):		Create RAID 5 (stripe with parity):
	mdadm --create --verbose /dev/md0 --level=5 --raid-devices=3 /dev/sd[~~cde~~]1		mdadm --create --verbose /dev/md0 --level=5 --raid-devices=3 --spare-devices=0 /dev/sd[bcd]1
	mdadm --create --verbose /dev/md0 --level=5 --raid-devices=3 --spare-devices=1 /dev/sd[~~cdef~~]1		mdadm --create --verbose /dev/md0 --level=5 --raid-devices=3 --spare-devices=1 /dev/sd[bcde]1

	Create RAID 10:		Create RAID 10: (mirrored stripe)
	mdadm --create --verbose /dev/md0 --level=10 --spare-devices=0 /dev/sd[bcde]1		mdadm --create --verbose /dev/md0 --level=10 --raid-devices=4 --spare-devices=0 /dev/sd[bcde]1
	mdadm --create --verbose /dev/md0 --level=10 --spare-devices=1 /dev/sd[bcdef]1		mdadm --create --verbose /dev/md0 --level=10 --raid-devices=4 --spare-devices=1 /dev/sd[bcdef]1

	Add partition to md device:		Add partition to md device:

Kenneth: /* Sample mdadm.conf */

2025-09-08T17:22:17Z

Sample mdadm.conf

← Older revision		Revision as of 17:22, 8 September 2025
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	devices=/dev/nvme0n1p1,/dev/nvme1n1p1,/dev/nvme2n1p1,/dev/nvme3n1p1		devices=/dev/nvme0n1p1,/dev/nvme1n1p1,/dev/nvme2n1p1,/dev/nvme3n1p1
	</pre>		</pre>

			=== descriptive names mdadm.conf ===

	or using descriptive names:		or using descriptive names:

	<pre>		<pre>
	#DEVICE partitions containers		#DEVICE partitions containers
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	# will create symlink /dev/md/big		# will create symlink /dev/md/big
	ARRAY big level=raid10 num-devices=4 metadata=1.2 spares=1 UUID=b14087e3:cf905322:9434e4af:6362e366		ARRAY /dev/md/big level=raid10 num-devices=4 metadata=1.2 spares=1 UUID=b14087e3:cf905322:9434e4af:6362e366
	devices=/dev/nvme0n1p1,/dev/nvme1n1p1,/dev/nvme2n1p1,/dev/nvme3n1p1		devices=/dev/nvme0n1p1,/dev/nvme1n1p1,/dev/nvme2n1p1,/dev/nvme3n1p1
	</pre>		</pre>

Kenneth: /* Commands */

2025-09-08T17:20:32Z

Commands

← Older revision		Revision as of 17:20, 8 September 2025
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	mdadm --create --verbose /dev/md0 --level=5 --raid-devices=3 /dev/sd[cde]1		mdadm --create --verbose /dev/md0 --level=5 --raid-devices=3 /dev/sd[cde]1
	mdadm --create --verbose /dev/md0 --level=5 --raid-devices=3 --spare-devices=1 /dev/sd[cdef]1		mdadm --create --verbose /dev/md0 --level=5 --raid-devices=3 --spare-devices=1 /dev/sd[cdef]1

			Create RAID 10:
			mdadm --create --verbose /dev/md0 --level=10 --spare-devices=0 /dev/sd[bcde]1
			mdadm --create --verbose /dev/md0 --level=10 --spare-devices=1 /dev/sd[bcdef]1

	Add partition to md device:		Add partition to md device:

Kenneth: /* Commands */

2025-09-08T17:16:16Z

Commands

← Older revision		Revision as of 17:16, 8 September 2025
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	cat /proc/mdstat		cat /proc/mdstat

	Show md device details:		Show md device details: (needs full path)
	# mdadm --detail /dev/md0		mdadm --detail /dev/md0
	mdadm -~~-detail md0~~		mdadm -D /dev/md/thebig

	Create RAID 0 (stripe):		Create RAID 0 (stripe):
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	# mdadm --stop /dev/md0		# mdadm --stop /dev/md0
	mdadm --stop md0		mdadm --stop md0
			mdadm -S /dev/md/thebig

	Start (assemble) array:		Start (assemble) array:
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	mdadm --verbose --assemble md0		mdadm --verbose --assemble md0
	mdadm -v -A md0		mdadm -v -A md0
			mdadm -v -A thebig

	Add disk to RAID 5:		Add disk to RAID 5:

Kenneth: /* Sample mdadm.conf */

2025-09-08T17:11:14Z

Sample mdadm.conf

← Older revision		Revision as of 17:11, 8 September 2025
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	MAILADDR root		MAILADDR root

	ARRAY /dev/md/md0 level=raid10 num-devices=4 metadata=1.2 spares=1 UUID=b14087e3:cf905322:9434e4af:6362e366		ARRAY /dev/md/md0 level=raid10 num-devices=6 metadata=1.2 spares=1 UUID=fc5714ab:ecb661c5:5abf4c99:ea07a6ba
			devices=/dev/sdb1,/dev/sdc1,/dev/sdd1,/dev/sde1,/dev/sdf1,/dev/sdg1,/dev/sdh1

			ARRAY /dev/md/md1 level=raid10 num-devices=4 metadata=1.2 spares=1 UUID=b14087e3:cf905322:9434e4af:6362e366
	devices=/dev/nvme0n1p1,/dev/nvme1n1p1,/dev/nvme2n1p1,/dev/nvme3n1p1		devices=/dev/nvme0n1p1,/dev/nvme1n1p1,/dev/nvme2n1p1,/dev/nvme3n1p1
			</pre>

	ARRAY /dev/md/~~md1~~ level=raid10 num-devices=6 metadata=1.2 spares=1 UUID=fc5714ab:ecb661c5:5abf4c99:ea07a6ba		or using descriptive names:
			<pre>
			#DEVICE partitions containers
			HOMEHOST <system>
			MAILADDR root

			# will create symlink /dev/md/fast
			ARRAY /dev/md/fast level=raid10 num-devices=6 metadata=1.2 spares=1 UUID=fc5714ab:ecb661c5:5abf4c99:ea07a6ba
	devices=/dev/sdb1,/dev/sdc1,/dev/sdd1,/dev/sde1,/dev/sdf1,/dev/sdg1,/dev/sdh1		devices=/dev/sdb1,/dev/sdc1,/dev/sdd1,/dev/sde1,/dev/sdf1,/dev/sdg1,/dev/sdh1

			# will create symlink /dev/md/big
			ARRAY big level=raid10 num-devices=4 metadata=1.2 spares=1 UUID=b14087e3:cf905322:9434e4af:6362e366
			devices=/dev/nvme0n1p1,/dev/nvme1n1p1,/dev/nvme2n1p1,/dev/nvme3n1p1
	</pre>		</pre>