> in between I learned how to setup a raid1 from existing data. Now I have
> one more question: If I decide some fine day that I need one disk of my
> raid1 for something different that the mirror, how can I destroy the
> raid1 and instead use one of the (old raid) disks as usual (non raid) disk.
You need to update /etc/raidtab and /etc/fstab to reflect the changes.
If you are using the latest boot-time auto-detection code, you simply change
the partition type from 0xfd to 0x83 to say that it is an ext2 partition.
If not, then there is nothing else to do.
Easy peasy !
> Can I keep the data?
Yes.
> I guess what has to be done somehow is to remove the persistent raid
> superblock somehow so that neither the kernel nor the raidstart tools
> recognizes the a raid configuration on one of the disks. Is this possible?
You should probably do this as well.
Note that this needs a *little* bit of care if you want to preserve the data.
I have a perl script which I use to manipulate and dump PSBs which flips a
couple of bits to `disable' it.
I WOULD IMAGINE (but I have not done it, so test it first) that you should be
able to set up the two devices as some other type of RAID device with a PSB,
e.g. as a `linear' device with one partition or a RAID1 device with a single
good disk (probably need a second, failed disk to keep it happy) which would
have the effect of over-writing the PSB with `harmless' data.
