how to create a degraded raid1 with only 1 of 2 drives ??

[Mitchell Laks <mlaks@post.harvard.edu>]

Hi mdadm raid gurus,

I wanted to make a raid1 array, but at the moment I have only 1 drive available. The other disk is
in the mail. I wanted to make a raid1 that i will use as a backup.

But I need to do the backup now, before the second drive comes.

So I did this.

formated /dev/sda creating /dev/sda1 with type fd.

then I tried to run
mdadm -C /dev/md0 --level=1 --raid-devices=1 /dev/sda1

but I got an error message
mdadm: 1 is an unusual numner of drives for an array so it is probably a mistake. If you really
mean it you will need to specify --force before setting the number of drives

so then i tried

mdadm -C /dev/md0 --level=1 --force --raid-devices=1 /dev/sda1
mdadm: /dev/sda1 is too small:0K
mdadm: create aborted

now what does that mean?

fdisk -l /dev/sda  shows

device boot	start	end	blocks 	Id	System
/dev/sda1 	1	60801	488384001 fd	linux raid autodetect

so what do I do?


I need to back up my data.
If I simply format /dev/sda1 as an ext3 file system then I can't "add" the second drive later on.

How can I  set it up as a `degraded` raid1 array so I can later on add in the second drive and sync?

Thanks for your help!

Mitchell