[CentOS] Turning root partition into a RAID array

Bryan J. Smith thebs413 at earthlink.net
Tue Nov 15 17:34:10 UTC 2005

Nigel kendrick <support-lists at petdoctors.co.uk> wrote:
> I have a CentOS 4.2 system that was set up VERY quickly
> following the demise of its former life as a CentOS 3
server -
> you don't want the full story, but it had to be done
> to get a company up and working following a slight disaster
> involving an electrician, a portable appliance safety
> and a pulled power cable - anyway, here's where I am at...

Er, um, would RAID solve that problem?  I.e., did you fry the
drive or get physical errors?  Or did the filesystem get
toasted?  I mean, drive failures are one thing, but
electrical/surges are a completely other thing (and RAID
might not help you there ;-).

> If I try and use mdadm right now I get complaints that
> /dev/hda3 is busy (fair enough) so I guess I need to be in
> less than 'full steam ahead' mode to make the change - over
> to you....

As many other people have pointed out, you'll need to have
the system off-line to do this.  The Rescue CD has pretty
much everything you need -- from mdadm to grub.  There are a
few HOWTOS, although I find some of their example hardware
configurations to be a bit disturbing (like putting an ATAPI
device as a slave to an ATA drive).

It used to be more of an issue when /boot (with the initrd)
couldn't be a md device, but that no longer seems to be a

-- Bryan

P.S.  I'll reiterate that a $100-125 3Ware Escalade 7006-2
(ATA) or 8006-2 (SATA) card gives you quite "piece of mind"
for the price when it comes to RAID-1.  And since it doesn't
use block striping (unlike RAID-0, 10 or 5), you can remove
the disks from the RAID-1 volume and use them without the

With 3Ware, you don't have the boot-time issues, you don't
have the ATA chipset/drive timeout issues, and the admin
tools do their job quite well (with more and more standard
support software like smartd being able to monitoring 3Ware
kernel message, etc... as well).

Bryan J. Smith                | Sent from Yahoo Mail
mailto:b.j.smith at ieee.org     |  (please excuse any
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