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Old 03-20-05, 06:13 PM   #2
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Join Date: Mar 2005
Posts: 33
Default Re: SATA-RAID with SuSE 9.x

Your question is twofold - (1)Is it hardware RAID or not and (2)How can I get it to work with Linux 2.6.x kernels.

(1): Yast is right - the A7N8X uses a software RAID solution.

How comes ? The Silicon Image 3112 SATA controller used includes a RAID BIOS, so it should be hardware, isn't it ? Well, in fact no.

Hardware RAID is when a dedicated controller does all the dirty RAID management job by itself - your Athlon CPU basically says "here is some data, write it to your connected disk" and the RAID controller splits them between disks. The CPU doesn't even know some RAID is involved. Hardware RAID is usually costly stuff used in servers and high-end machines.

The Si3112 (as most of the cheap RAID controllers sold) doesn't do that job. In that case, it is your Athlon CPU that does all the computation by itself. The SATA controller is only an interface with the connected disks, just like any ordinary IDE controller.

The only use of the RAID-BIOS of the Si3112 is to allow access to the RAID array in real mode (the mode in which an x86 computer initializes itself), so you can use it as a bootdisk. It is of no use under 32-bit operating systems like Linux or Windows - that's why both of those need special drivers to work.

(2)To access to the content of the array under Linux, you have to use the dmraid tools.

2.6.x kernels manage those arrays "in userspace" for various reasons. The program to use is called dmraid. If you want to boot from a RAID array, you'll have to use that tool. If your root partition is on the RAID array, you'll have to create an initrd image including that utility.

Notice that unless you want to share your RAID content with Windows, you're better off using the Linux Software RAID driver - it performs better and is more flexible, as you can spawn the array regardless of the controller the disks are connected on (for example, my own RAID-0 array extends to 2 SATA drives on the Si3112, one ATA133 on the nForce2 and one ATA100 on a Promise PCI add-in card).

SuSE-provided information:

Hope this helps !
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