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Re: Help with RAID and Formating Disks

Quoting Michael Acklin <freeop@swbell.net>:

Hello all. I am very new at what I am attempting to do. I have run
Debian in the past and just recently installed it on a new built system
that I am setting up. So please take it easy on the Newbie.

First I built the system with the ASUS Motherboard and AMD-64x2 5800+.

Added 3 - 500gig drives and a DVD/CD writer to access the Downloaded
netinst of Debian. The installation went fine with no problems over the
internet installation. Added all the programs that I thought I would
need and finished the installation. During the installation process it
formatted /dev/sda as ext3 and used the complete disk for the
system/files. I was never given the opportunity to format/partition the
second and third drives. Figured I would get to that when I set up the

Anyway tried using mdadm but am at a loss what I am trying to do. I
tried the parameters that was called out in the --help file, but kept
getting "not enough devices" errors. I believe the command line I used

mdadm -create /dev/md0 -l 5 -n 2 -x 1 -c 32

and in different combo's of the above.

From what I can tell, you successfully installed debian to your sda drive and booted it. Now you want to setup a raid array (from your 2 remaing disks) so that you can mount it somewhere on your system. Correct?

There are some fundamentals missing here.
You attempted to build a raid 5 array, which requires a minimum of 3 disks.
If your sda is entirely used up as your bootable system, you can't use it elsewhere. Having said that, mdadm is a powerfull raid tool which will allow
you to use paritions of disks in your raid array, instead of the entire disk.
Try looking in /usr/share/docs/mdadm for more info.

I then figured that as /dev/sdb and /dev/sdc where not partitioned or
formatted, I should do that. But that is where I am completely lost. I
have no idea how to format or partition the other drives.

Tried finding some tools that might help out, but couldn't find
anything that might help. I know I am not using the terminology
correctly to search for the right tools. So came here to see if anyone
could help out.

So I guess my question is: Do I have to format/partition each of the
drives before making a RAID or can the mdadm program do this. And what
is the easiest way to set up the RAID.

Thats right,
Your disk will need to be partioned and the partitions need to be setup as type "Linux Raid Autodetect" partitions. cfdisk is a great tool for this.

Again, check the mdadm man page or its docs. Lots of good stuff there.

Since you have a bootable system, with 2 remaining unused disks, try making a raid 0 or raid 1 array. For example, something like:

# cfdisk /dev/sdb
# cfdisk /dev/sdc
# mdadm -C /dev/md0 -l 0 -n 2 /dev/sdb1 /dev/sdc1


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