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I ran these commands:

$ sudo mdadm --verbose --create /dev/md0 --level=10 --chunk=256 --raid-devices=4 /dev/sdh1 /dev/sdh2 /dev/sdh3 /dev/sdh4
$ echo 'DEVICE /dev/sdh1 /dev/sdh2 /dev/sdh3 /dev/sdh4' | sudo tee -a /etc/mdadm.conf
$ sudo mdadm --detail --scan | sudo tee -a /etc/mdadm.conf

It seems that my system can no longer find the RAID device after reboot.

Running mdadm -Q /dev/sdh1 outputs

/dev/sdh1: is not an md array
/dev/sdh1: device 0 in 4 device unknown raid10 array.  Use mdadm --examine for more detail.

and mdadm -Q /dev/md0 outputs

mdadm: cannot open /dev/md0: No such file or directory

My /etc/rc.sysinit has this line:

# Start any MD RAID arrays that haven't been started yet
[ -r /proc/mdstat -a -r /dev/md/md-device-map ] && /sbin/mdadm -IRs

I'm not sure what this does but I do not have a /dev/md directory. I'm running an Amazon Linux.

Any advice on what I can do? Could the kernel have renamed the RAID device? Should I modify my rc.sysinit file?

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For raid to make any sense, several drives must be used. Are /dev/sdhX partitions on the same drive? If they are, you're doing it wrong. – Ярослав Рахматуллин Nov 9 '12 at 2:48

The array must be re-assemple from the member drives when booting. This can be done with:

mdadm -A /dev/mdx /dev/parti /dev/partk /dev/partn [...]

It is usually more convenient to do this automatically in /etc/mdadm.conf:

DEVICE /dev/sd*

ARRAY /dev/md2 level=raid10 num-devices=4 metadata=0.90 UUID=b9de52aa:2907a6ca:5c45245c:9d6efa15
ARRAY /dev/md1 level=raid1 num-devices=4 metadata=0.90 UUID=f9d44a97:e751f917:e8628a2d:b6e629f3
ARRAY /dev/md3 level=raid0 num-devices=4 metadata=0.90 UUID=2aa775b8:35cfe1c0:25d36f80:9c6df7c4
ARRAY /dev/md5 level=raid10 num-devices=4 metadata=0.90 UUID=db8bc05d:ca12cbfc:4c6759c5:2c647efc
ARRAY /dev/md6 level=raid10 num-devices=4 metadata=0.90 UUID=10b5e3c9:b5c54ccc:c588f210:baae4ad8
ARRAY /dev/md50 level=raid5 num-devices=3 metadata=0.90 UUID=2ba30d45:fa43a215:60c02926:be4d01ef
ARRAY /dev/md7 level=raid5 num-devices=4 metadata=0.90 UUID=7bd7830f:bcc40674:6821c544:014da426

For reference:

http://aws.amazon.com/articles/1074

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