Easy Software Raid For Linux

[astrocrep]

I searched for hours to find this out, so I figured I would post it for those interested.

This applies to people who want to setup a raid array(s) to BOOT linux off of.
This ONLY applies to nForce Motherboards (probably just nf4)

Distrobution considerations: Its best to use a distrobution that has a textmode install. Using the LiveCD version of ubuntu, I was not given a choice to setup raid. Textmode FTW!

The method below worked perfectly on Fedora Core 5-64bit and Ubuntu 6.06 F7-64bit (textmode installs only)

Step 0.) Remove all storage devices NOT included in the Array.

Step 1.) Disable Raid Support in Bios and and other type of "Software" Raid Controller. That nifty nforce 4 motherboard you have DOES NOT have a HW Raid controller. You will find that if you use that raid controller and try to get linux to play nice, you will fail miserably!

Step 2.) Ensure dmraid is NOT Running! When picking your destination device if you see something along the lines of /dev/mapper/nvida_***** then its running. Reboot your installation cd and add "nodmraid" to the kernel boot command line. This was Off by default on Ubuntu 6.06 Flight 7 and On By default on Fedora Core 5.

Step 3.) Partition creation. As an example, I will use my personal setup.
/dev/sda - WD Raptor 10k 37gb
/dev/sdb - WD Raptor 10k 37gb

/dev/sda
P1: (size) 100mb (type) software raid
P2: (size) 1024mb (type) linux swap
P3: (size) 36GB (type) software raid

/dev/sdb
P1: (size) 100mb (type) software raid
P2: (size) 1024mb (type) linux swap
P3: (size) 36GB (type) software raid

Step 4.) Now select Raid setup from the Partition Tool (super easy in ubuntu or FC5). You will be making 2 Arrays. Array 1 (called /dev/md0 in most cases) will be /dev/sda1 and /dev/sdb1 and will be a Raid 1 Array *** This is Hella Important! Why Raid 1!?!?! Theres no speed increase you say!!! Well my friend, GRUB could care less about whatever software raid array you got setup, so we need to make sure grub can boot our system, and since its just a RAID 1 (Mirror) it can "boot" /dev/sda1 as if it was a single normal HDD. Format this array as ext3 and mount it as /boot and make it bootable. Now for your second array, Array 2. Select partitions /dev/sda3 and /dev/sdb3 and make them a Raid 0 array (yea!!) format it as however you want, I did ReiserFS and mount it as "/".

Step 5.) Grub will most likely be installed without intervention from you if required, have it install on /dev/sda.

Step 6.) Install as normal.

Step 7.) Reboot.

Step8.) Brag to your friends that you've got a Raid 0 array for booting linux!

Thats it!

Extra Info:
- Both of your swap partitions should be active by default.
- When I hooked up my 320gb SATA it became the New /dev/sda and pushed my other two drives down to /dev/sdb and /dev/sdc... the only thing I had to fix was the fstab for swap partitions.
- When hooking up your other drives make sure bios boots the right drive.

Good luck!

If you got any question post.

Thanks,
Rich

[Aynjell]

DMraid is the software for nforce4 boards. I'd rename your thread to all chipsets in general, since mdraid is fully software, whereas dmraid is for nforce boards.

[astrocrep]

I had issues gettting DMRaid to work...

Perhaps if I try it again...

Would I see a difference in performance between DMRaid Vs. MDRaid?

Thanks,
Rich