Linux Hardware RAID Configuration

[Craig White]

On Sun, 2006-03-05 at 16:16 -0700, Jeff Garland wrote:
> Darrin Chandler wrote:
> 
> > If it's *really* hardware raid then you'd only see 1 disk. You can only 
> > see the disk at all through the controller, after all. So the controller 
> > isn't taking over at that level. 
> 
> This is my suspicion...and what you are saying validates what it says in:
> 
> http://www.linuxhomenetworking.com/linux-adv/raid.htm#_Toc92809999
> 
>    Hardware RAID configuration is usually done via the system BIOS
>    when the server boots up, and once configured, it is absolutely
>    transparent to Linux. Unlike software RAID, hardware RAID requires
>    entire disks to be dedicated to the purpose and when combined with
>    the fact that it usually requires faster SCSI hard disks and an
>    additional controller card, it tends to be expensive.
> 
> So I'll goof around with the bios settings a bit to make sure I have 
> them right.
> 
> > You may have one of the SATA 
> > hardware/software combo raid systems that have been going around (I have 
> > one). If your OS doesn't support it then you can't use it as raid. I'm
> > not at all sure of Ubuntu. 
> 
> The system doesn't have an OS yet.  I've been experimenting with a few 
> distros as I'm ready to give up on Mandrake that I'm using for eons and 
> try something else.  So far it's been mostly problems.  The straight 
> Debian 3.1 R1 hangs on the install, Ubuntu 64 bit Live CD (acquired as a 
> prize at the Dev meeting the other night, Thx!) blows up on the X 
> startup.  So I was trying the Ubuntu 64 bit installed CD to see if I 
> could work out an X config.  I've long since passed my usual tolerance 
> for this sort of 'fun'....but I digress...
> 
> As for the RAID support, Ubuntu clearly has it, but I think what they 
> are talking about is Software RAID where the hardware isn't used.
> 
> > I know there are drivers and stuff for it for 
> > Linux, but I don't have any details. I believe the guys at Linux 
> > Certified will ship that way as an option. Wish I had more to tell you.
> 
> Thx -- every little bit helps.
----
a lot of the supposed 'RAID' controllers aren't really hardware RAID at
all but are entirely software driven. Very few are supported by Linux
kernels and only some of them have Linux 'drivers' available that you
could actually use to install Linux on them. I have heard them termed
'Fake RAID' in that they really aren't hardware raid at all.

If the BIOS doesn't completely support setup of RAID system volumes,
then it makes little sense to put yourself into a situation where you
will depend upon drivers from vendor to use software raid when you can
use software RAID built into virtually every Linux distribution and be
able to upgrade without worrying about getting updated driver and it's
probably faster too.

Craig