# Raid on Intel(R)Workatation Board S5520SC

## fernandoc1

I have a Intel(R)Workatation Board S5520SC that have hardware RAID support on BIOS. 

When I create a Virtual Disk, merging two HDs, on it's RAID Utility it is recognized by MS Windows as single disk with the amount of space equals to the sum of the two identical hard disk that are installed there.

But I need to install Gentoo on it and when I boot into the live CD, I get my disks mapped independently as /dev/sda and /dev/sdb.

It also happens on Ubuntu.

Is there any way to get these disks merged into the RAID array on Linux?

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## NeddySeagoon

fernandoc1,

First, do don't have hardware raid. Your raid is software raid, provided partly by your BIOS and partly by Windows drivers.

Its somewhat unkindly called fakeraid, as it looks like hardware raid to Windows users but its not.

To use in in Linux, you need a system with dmraid support. Exactly what that means depends on if you will have your linux root partition on the raid or not.

IF you start the Gentoo liveCD with the dodmraid option, you should see your two separate  drives still and also /dev/mapper/... which contains your raid partitions.

dmraid support cannot be built into the kernel, so root on dmraid requires the use of an initrd.

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## fernandoc1

As I can see, then, there is no advantage in enabling RAID on BIOS.

If I disable RAID on BIOS and follow the steps on http://www.gentoo.org/doc/en/gentoo-x86+raid+lvm2-quickinstall.xml I will get the same results as RAID was enabled on BIOS?

And another question: is there a true Hardware RAID?

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## NeddySeagoon

fernandoc1,

Yes but you will not be able to share the raid with Windows.

dmraid allows both Windows and Linux to use the raid.

Hardware raid can be shared, provided both systems have hardware drivers

Kernel raid is linux only

Windows dynamic disks can be shared with linux

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## fernandoc1

I wish to have an Hard disk organization that is capable to automatically backup data to another disk.

What do you suggest me to do?

My disks should be in a state that if one disk fail, the other must have the exact copy of the other, in a way that any one can easily and quickly get the system running again.

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## NeddySeagoon

fernandoc1,

If your system will not include Windows, use kernel raid1.  Its faster than dmraid and its portable across hardware.

If you must have windows, you have the choice of Windows Dynamic Disks or dmraid.

With raid1, if a disk dies, the sysem will carry on working on the remaining disk.

You must also put swap on raid1.

Raid is not a backup. rm <very_important_file> removes the file from all drives. You still need your backups.

Raid provides redundancy against drive failure.

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## fernandoc1

Ok, thanks for your suggestion.

I will not need Windows - and I expect to never need to use it on my whole life - but I only mentioned that to compare the differences on the behavior of the systems while I was trying to set up the RAID.

Initially, I though that BIOS RAID created a Virtual Device that should be seen on the operating system as unique hard disk, like in the Windows disguise.

With your explanations I have a better idea of what is happening.

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