From Sigmon

quick howto

apt-get install -y mdadm

Assemble an array

mdadm --assemble /dev/md0 /dev/sd[bcdef]
mdadm --detail --scan >> /etc/mdadm/mdadm.conf

mkdir -pv /data
mount /dev/md0 /data

grep /data /etc/mtab  >> /etc/fstab

$ dmesg |grep kick

[  547.114433] md: kicking non-fresh sdf from array!
[  547.141308] md: kicking non-fresh sdb from array!

re-add failed drives

/sbin/mdadm /dev/md0 --fail /dev/sda5 --remove /dev/sda5
/sbin/mdadm /dev/md0 --add /dev/sda5

beware order of reassembly

<nevyn> sigmonsay: more precicely if you had an array with disk A B C D
<nevyn> sigmonsay: the trick is.
<nevyn> if the array ejects B continues degraded (but one failure is non-fatal)
<nevyn> and then ejects D
<nevyn> if you reassemble the array with ABC then D then much badness happens
<nevyn> if you reassemble with ACD then B then it's fine

Initiate self check

/usr/share/mdadm/checkarray --idle md0

random

rescan scsi bus

    echo "- - -" > /sys/class/scsi_host/host0/scan