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Linux + RAID array?

Posted: Sun Jul 31, 2005 7:26 am
by Jeff250
I've got an SATA RAID 0 array (via an Intel ICH7R southbridge) with already a Windows partition (from which I'm humbly typing) plus 36GB of unpartitioned space that I'd like to use toward an Ubuntu 5.04 installation. I tried using the Ubuntu setup CD to install it, but the setup seemed to detect the drives in the array seperately instead of as a part of an array and didn't seem able to detect the NTFS partition already present either (much unlike its success with my IDE "storage" drive). As much as I like causing partition plunder, I felt hesitant about advancing any further in the setup process. :P

Now, of course, this comes as absolutely no surprise, since even a Windows setup requires the Intel RAID drivers via floppy disk (or, as I soon learned to do, via my own "tweaked" installation CD). But I'm still at a complete loss as what to do next. Any Linux gurus here willing to lend a few words of advice? Microsoft always included that nice F6 key. :oops:

Posted: Sun Jul 31, 2005 8:34 am
by Admiral LSD
"Firmware" RAID devices like most all integrated motherboard controllers are notoriously finicky under Linux. Since they rely on software drivers for a lot of the magic much like WinModems the driver support is often in a greater state of disarray than normal. Usually, the best way to approach RAID under Linux with these controllers is to forget about any alleged RAID capability the device offers and simply go for Linux software RAID, it saves a lot of headaches.

Posted: Sun Jul 31, 2005 12:21 pm
by FunkyStickman
Like LSD said, Linux works best with a straight-up hardware or software RAID. (Highpoint 404/454 cards are bad about this, too). Since Linux detects the drives separately, that means they're not in a "real" hardware RAID mode. You'll probably notice that your CPU usage is higher when you do disk-intense operations: that's because it's using software drivers.

You can still install Linux with software RAID on the two drives. You didn't mention which version of Windows you're using, I'm guessing it's XP or 2K. You should be able to access it once you install Linux, however, I don't think you can boot Linux from a RAID 0 array. That means you'd have to create a non-RAID boot partition, and it more than likely won't be able to access the MBR on the striped Windows partition to boot from anyway.

You could feasibly create a Linux boot floppy with the RAID drivers, but that's probably more work than you're wanting to do. Your best bet would be to stab in a cheap extra drive and use that for Linux. If you're trying to dual-boot with striped arrays, it will only end in tears unless it's 100% pure hardware RAID.

If anybody has info to the contrary, please feel free to speak up. I'd be interested in hearing how it's done.

Posted: Sun Jul 31, 2005 1:45 pm
by Jeff250
In my Google quests, I kept running into some tool called dmraid. Anyone know if it would help?

I suppose that if the hassle far outweights the benefit, I could just repartition some space on my IDE drive.