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Re: Fatal: Only RAID1 devices are supported as boot devices

Mathieu Malaterre put forth on 12/4/2009 2:55 AM:

> That's extremely clear indeed ! The issue is that I was confusing
> software RAID and hardware RAID. So I rebooted the system and in the
> BIOS I setup the RAID0.
> It now shows up as "DELL Virtual Disk" with 6Tb of disk (4 * 1.5Tb).
> What I do not understand is why the very first disk is visible...
> Should I install the /boot in this one ?

I think you are still missing the big picture.  Techno mumbo jumbo about
RAID and that big phat 6TB "disk" you see is making your crotch tingle,
making you wanna hump your computer.  You apparently have more money and
disk space than common sense.

WAKE UP!  Never, ever, install /boot, or the root filesystem, including
all the usual stuff like /bin, /sbin, /etc, to a stripe set without
parity.  This includes RAID 0, which IS NOT RAID at all!

Since you seem allergic to reading about RAID on say wikipedia or such,
I'll explain it in simple terms:

You have one disk in the system.  If it fails, your system fails.  So
the chance of system failure is disk_fail_probability x 1.

You have 4 disks in your system in a RAID 0.  If one disk fails your
system fails.  So the chance of system failure is 4 x
disk_fail_probability x 1.

Thus, your system with your boot and system files sitting on a hardware
RAID 0 (stripe) across four disks IS 4 TIMES AS LIKELY TO FAIL compared
with having only one disk.


With the LVM solution already mentioned in a previous post, you should
be able to partition a small amount of space, say 50GB, mirrored across
all 4 disks, on which you'll install /boot and the system.  Then, you
should also be able to use the rest of the space on all 4 disks to
create a stripe set.  I know the Linux capability exists to do this, but
I've never done it myself.  So, I can't spoon feed you the instructions.
 Google is your friend here.  Maybe some other kind sole on debian-users
can help you out.

But, I'm telling you with authority, this is how you need to set up your
four 1.5TB drives.  Doing this, 3 of your 4 drives could fail, and your
system will still boot and be intact.  You could then add 3 more
replacement disks and setup everything again.  However, as you should
already know, you will lose all the data on that big phat 5.8TB stripe
set (RAID 0).

Heed the warnings and do what must be done.


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