Re: mdadm without initramfs
On 08/16/2010 08:14 AM, Stan Hoeppner wrote:
Boyd Stephen Smith Jr. put forth on 8/15/2010 5:34 PM:
In<20100815190053.GA4521@gandalf.home.lxtec.de>, Elimar Riesebieter wrote:
How do I set up mdadm to create the root array witout an initramfs?
You can't. mdadm is a user-space binary that can't be compiled into the
kernel images. Therefore, to run mdadm you need an initramfs, or the file
system containing '/' must already be mounted by the kernel.
Last I checked, it is possible to have the kernel itself start the root array,
via a (series of) kernel command-line arguments. However, this doesn't use
mdadm or any of its configuration files.
Similarly, mdadm doesn't read the kernel command-line, so it is possible the
configurations to diverge. It may be possible to have a GRUB2 hook to
generate the kernel command-line arguments from the mdadm configuration, but
I've not seen such a hook. In the absence of such a hook (or when you are not
using GRUB2 as your bootloader), you should simply use an initramfs.
This has always been one of my hangups regarding using linux mdraid (or any
soft OS raid) vs hardware raid--proper and seamless handling of a raid
protected boot device, including issues beyond the topic of this thread. I
hate admitting it, but Microsoft's implementation of a mirrored boot/system
disk is supremely simply compared to getting the same thing from Linux.
Matter of fact, setting up any type/level raid in Windows is much more
straightforward. And I'm not a big Windows fan, far from it.
I prefer LSI and Intel raid cards. I should have said merely LSI as the Intel
cards are licensed LSI cards. Hardware raid isn't as flexible as softraid as
it works at the entire disk level, but boy is it so much easier to work with,
as much faster. The single biggest advantage to hardware raid is that you
don't have to disk with changing bios boot order or anything like that if you
have to reboot while drive in your boot array is offline/down/dead. It's all
I haven't messed with windows since xp. But I do remember on xp you
could not have any software raid on the same partition that you booted
from. Which made it pointless... Did they change the functionality in
vista or 7 or something?
As far as I know, mdadm is maintained by only one man. So we better just
be thankful that we have it!