Re: [gentoo-user] How to get raid

[Jeff Cranmer]

On Thu, 2012-01-05 at 04:01 +0100, Volker Armin Hemmann wrote:

> the short one:
>
> partition one disk with (c)fdisk. Use sfdisk to transfer the partition scheme
> to the other disks.
>
> run mdadm --create /dev/md0 level=whatever you want --raid-
> devices=thenumberofdevices /dev/sdXY /dev/sdZY ...
>
> mdadm --detail --scan >> /etc/mdadm.conf
>
> done
>
>
OK, but there is active data on the disks, so I don't want to partition
them.  They should already partitioned, and running fdisk will erase the
data.

If I run mdadm --create /dev/md0 level=5
--raid-devices=3 /dev/sdb /dev/sdc /dev/sdd, will that erase data
already on the disks?

Prior to running this command, there is no /dev/md entry.  Is this
correct?

Looking further by using fdisk, it appears that sdc has a linux
partition on sdc1 starting at sector 34, and a GPT partition of size 0+
at /dev/sdc4, sector 0.  Nothing else is on that disk (no sdc2 or sdc3).

sdd and sdb report invalid partition table flags and do not appear to
have active partitions.  Does this make sense?

Is it possible that I ordered the disks incorrectly when I installed
them, and by simply swapping disks b and c at the raid I can get things
to start making sense?  Is there an order to a set of RAID5 disks?  I
thought any two of three RAID5 disks could be recovered, regardless of
which one dies?
 
> there is a reason why I never ever touch genkernel.
>
> you should forget that crap. You don't need to copy around anything. If your
> root is not on some fancy setup, you don't need initramfs.
>
> Just make a nice kernel, put it in /boot. Done.
>
OK.  The OS disk is non-RAID (120GB SSD), so I don't need any fancy
options in my kernel. All the domdadm and dodmraid stuff is needed just
when your OS disk is raided.  Correct?

Thanks

Jeff