RAID 1

[GeraldCC]

On Saturday, October 09, 2010 11:22:28 am Tom H wrote:
> On Thu, Oct 7, 2010 at 6:19 AM, GeraldCC <gcsgcatling at bigpond.com> wrote:
> > Is raid 1 safe to use in Ubuntu/Kubuntu?
> > I am reading the Ubuntu Server Administration (8.04 LTS)
> > Raid 1 appears to be recommended in this tome, but trying it in PCLinuxos
> > 2010.07 has given a lot of heart ache. If one removes the second drive in
> > the array, then powers up again the system still runs BUT shutting down
> > again and re-inserting drive 2 and trying to add it to the raid array I
> > need to reformat the first drive to add the second and also format the
> > second drive...So loosibg everything.
> > This does not seem to be the case in Ubuntu?
> > But is it OK and safe to use raid 1?
> 
> I've never used PCLinuxOS but I doubt that you lost everything because of
> it.
> 
> Assume that you have your system's root on /dev/md1 constituted of
> /dev/sda1 and /dev/sdb1.
> 
> If you shutdown the box, pull out /dev/sda, and reboot, the box will
> come up (assuming that grub is set up properly) using /dev/sdb1. If
> you then shutdown, re-insert /dev/sda, and reboot, the box will come
> up using /dev/sdb1 with /dev/sda1 available (and possibly even
> assembled into its own, new, one-disk RAID 1 md device, /dev/mdX). If
> /dev/sda1 is a member of /dev/mdX, you have to run "mdadm --stop
> /dev/mdX", otherwise you can skip this step. You then run "mdadm
> /dev/md1 --add /dev/sda1" to add /dev/sda1 to /dev/md1. You have to
> ensure that the mirror syncs before pulling any disk out again.
> 
> The proper way to remove a disk from an array is, even if disk dies,
> to run "mdadm /dev/md1 --fail /dev/sda1; mdadm /dev/md1 --remove
> /dev/sda1".
Thank you Tom,
I have printed out you reply so that I have it on hand.
On re-reading The book I saw the parts you were refering to. At the time of 
playing with PCLinuxOS I was not sure what I could do with raid 1. At least I 
understand a little bit more.
Again many thanks.
Gerald