CentOS + RAID with mdadm


RHCE exam requires you to be able to create a RAID array on a running system, as well as with the installer.

I won’t explain here how to deal with the installer as it’s pretty easy.

1. create the partitions

Using fdisk or else Set the ID type to “fd” (Linux RAID autodetect)

Say we got here /dev/hda2 and /dev/hdb2

2. create the RAID array with the first drive only

mdadm –create /dev/md0 –level=1 –raid-devices=2 /dev/hda2 missing

That’s my way of dealing with the creation of an array. You can obviously create the array with the 2 drives now.

3. Formatting the new array in ext3

mke2fs -j -c /dev/md0

-j for ext3 -c for check

4. Adding the other drive to the array

mdadm –add /dev/md0 /dev/hdb2

You should hear the drives working. They are actually synching Type : cat /proc/mdstat to see what is actually happening.

5. Edit fstab

Edit /etc/fstab

Add a line to get the array mounting when the system boots

/dev/md0 /raid ext3 defaults 0 2

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