March 24, 2017 | 9:59 am
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[HOWTO] use mdadm to create a raid 1 array

Ok, you have your 2 shiny brand new sata harddrives and want to set them up in a raid 1 (mirror) configuration?

# fdisk -l

This will list all the drives and partitions.  The 2 new drives should appear as new disks with 0 partitions on them.  In my case, the drives are /dev/sdc and /dev/sdd.

# mdadm –create –verbose /dev/md0 –level=1 –raid-devices=2 /dev/sdc /dev/sdd

Running that command will start the sync process and create the raid device, /dev/md0

# cat /proc/mdstat

Run the above command to view the status of the resync.  It will show a little progress bar, a percentage complete, and an estimated finish time.  On my box, it takes about 45 minutes to mirror 320Gb drives.

You can format, and start using the /dev/md0 device right away, even while it’s syncing.  The syncing goes on in the background all the time so you might as well get started.

That should be it.