how to use hardware RAID1 in 2008 beta2 gentoo[SOLVED]

upengan78 · l33t Joined: 27 Jun 2007 Posts: 711 Location: IL

Hi,

I have Optiplex 755, it has RAID controller utility where I have created an array for 2 samsung 160 G disks. RAID1.

I have set Drives as Autodetect RAID1 with ATA. There are other options such as RAID1, Autodetect Raid with AHCI and Legacy.

I would like to use the hardware RAID level 1 and install gentoo. For some reason I can not install in right device.

I tried with above hardware set and installing in /dev/sda and that did not boot OS. it showed weired characters in place of boot loader. when I had installed boot loader on /dev/sda it did not show any errors.

when I used legacy drives I get non mirrored gentoo.

Please guide for using this Hardware RAID( Intel Matrix Storage Manager)

Thanks

aceFruchtsaft · Posted: Fri Jun 20, 2008 3:06 pm Post subject:

The problem is that the RAID provided via the Intel ICH chipsets is NO hardware RAID. The RAID functionality is entirely implemented via the driver, and Linux in general does not support this. Therefore, in Linux you will not see one single RAID device but rather all disks separately.

Unless you want to dual boot with Windows, there is no reason to configure the RAID in BIOS; use Linux's own device mapper instead. If you want to dual boot, you'll most likely run intro trouble. If you are lucky, you can use dmraid (search the gentoo-wiki, Google, etc..). I tried this once with Intel's ICH8R, failed, and just bought a real hardware RAID controller. This was 1,5 years ago, so you may be more lucky.

NeddySeagoon · Posted: Fri Jun 20, 2008 4:08 pm Post subject:

upengan78,

Your RAID controller is not hardware raid, its software (int eh BIOS) raid, often called fakeraid.
The only reason to use fake raid is that linux and windows must share the raid set.

Boot the gentoo liveCD with the dmraid kernel option if you want to go this route. You probably don't, because kernel software raid is better.

For software raid, you need mdadm and the kernel raid modules for the raid personalties you want to use.
With kernel raid, you donate partitions, not drives to raid sets, thus you can mix several raid levels on the same drive.
Hint: you cannot boot for a kernel raid 0 set, so you must make /boot either raid1, or not raided.
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

upengan78 · l33t Joined: 27 Jun 2007 Posts: 711 Location: IL

Thanks for replying guys !

Well I have got something working using the wikis...nvidiaraid and others..

what I did is

NeddySeagoon · Posted: Tue Jun 24, 2008 6:45 pm Post subject:

upengan78,

Its BIOS raid or fakeraid and it is working

One of the reasons to not use fakeraid is support. The physical data layout on the drives is BIOS dependant.
You can only expect to read those drives with the same fakeraid chipset and the same BIOS. Other BIOSes and other chipsets do it differently.

Kernel raid is BIOS and chipset independant - you can plug a kernel raid set into other hardware and be confident you can read it.
You may not be able to boot from it but you will be able to read it.

Speed wise, fakeraid is little different from kernel raid as both are software raid implementions.
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

danomac · Posted: Tue Jun 24, 2008 8:37 pm Post subject:

Just a tip to add: if you forget to add 'dodmraid' you can modprobe it manually later in a shell and execute 'dmraid -ay' - this will detect your raid arrays without having to reboot.

Just installed a fresh install myself.

The only reason I had to do it this way is because Vista is on another partition, or I would've stuck with in-kernel raid.