Ubuntu & RAID

Liam Proven lproven at gmail.com
Tue Jan 13 16:47:19 UTC 2009

2009/1/11 Stephen Carter <stevecarter at fastmail.net>:
> Pierre Frenkiel wrote:
>> On Sat, 10 Jan 2009, Stephen Carter wrote:
>>> So, I burnt the iso to a CD and started the LiveCD process.
>>    for RAID, it's better to use the alternate cd.
>>    I installed 8.10 with RAID1 on several machines, and everything work perfectly,
>>    even in degraded mode.
>>    The best doc I know is:
>>      http://www.iki.fi/kuparine/comp/ubuntu/en/raid.html
>>     just ignore the grub-install call, and the bug mentioned at the end:
>>     it's no more true in 8.10.
> Pierre,
> Thank you for your response earlier today. I have been out and unable to
> reply until now.
> The onr big difference between what you suggest is that I want to
> install Ubuntu onto a pre-existing RAID 1 that is already configured
> into 4 partitions under Windows XP Pro.

Ah. This is critical information which you should have given at first;
your original post was thus very misleading.

The answer is: you can't.

A true RAID controller costs as much or more than a typical hard disk
and creates and manages the arrays in its firmware.  No disks are
attached to the motherboard controller, the PC BIOS sees no disks, and
the OS only talks to the RAID controller, seeing just the arrays - the
OS cannot see the disks themselves, except through special
vendor-specific RAID monitoring tools which interrogate the

You have a /firmware/ RAID, created by a driver in Windows working
with software in the PC BIOS or an additional BIOS.  These are cheap
and simple.

This is not compatible with Linux and you cannot share such an array
between different OSs.

Linux can use some software RAIDs but it is a very bad idea; Linux's
own built-in RAID support is considerably better. Even so, I would not
expect a Linux firmware RAID to share disks with a Windows firmware

Software RAID only exists because MS cripples workstation editions of
Windows by removing the RAID functionality of Windows Server. This is
a marketing decision; such things don't apply to Linux.

Your best option is:

Break the RAID, use Windows on one disk, Linux on another.

Liam Proven • Profile: http://www.linkedin.com/in/liamproven
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