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In BIOS, under SATA Configuration I can choose IDE, AHCI or RAID. Normally I choose RAID. After finished installing Windows 7, I wanted to setup RAID 1 (mirror), but Windows' disk management only showed me 1 disk (instead of two). Also, it said "no" under fault tolerance.

In fact, during the installation only disk 1's partitions were shown (disk 2 is unpartition).

I want to dual boot two systems. Should I change RAID to ACHI under the configuration prior to Windows 7's setup? I think software RAID is better (in general)? What is the best option (since doing dual boot).

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The RAID functionality in the BIOS and the RAID functionality in the OS are independent of each-other.

If you setup the RAID1 in the BIOS, then the motherboard's RAID controller does the mirroring, and shows it to the OS (Windows or otherwise) as a single drive.

The OS needs to do nothing special to use or manage the RAID (the RAID controller does it), so it's OS-independent.

The mirroring/spanning/striping in Windows is OS/software level, and it is generally used when there is no hardware RAID controller available. In this case the OS is responsible and you would have a hard time having both Linux and Windows use the same mirror, as they would both be trying to control it differently.

So turn it on in your BIOS, and then only expect to see one drive when installing an OS that supports your firmware RAID controller. :)

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    techie007 is correct. If you want RAID 1 protection for both OSs, you need to do the BIOS level RAID1 to make your disks fault tolerant. Then you can split the RAID into two volumes for Windows and Ubuntu.
    – Keltari
    Commented Sep 17, 2011 at 20:04
  • @techie007 thanks for the answer. yes. now a follow-up question. i can setup the raid 1 via BIOS. If I use GParted (a partition tool) to make several partitions prior to WIN7 installation, is that legal and recommended? Thanks
    – CppLearner
    Commented Sep 18, 2011 at 17:25
  • @JohnWong I'd say that's better asked as a new question. You can 'legally' partition your hard drives however you'd like. :)
    – Ƭᴇcʜιᴇ007
    Commented Sep 18, 2011 at 18:19
  • thanks. i will:) ur answer is very helpful, however.
    – CppLearner
    Commented Sep 19, 2011 at 5:14
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If you are going to use the BIOS RAID, you need to use it, and therefore you need to setup the RAID 1 partitions in the BIOS. At least, that's how it's been when I've used motherboard RAID, which I generally steer clear of (because if you change motherboards, you might be screwed).

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  • but the question is, if i dont enable bios raid, will i be able to do mirroring on windows 7? and is that a problem in trying to dual boot (hence, raid-1 for both win 7 and ubuntu)? thanks e40.
    – CppLearner
    Commented Sep 17, 2011 at 18:39
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    If you do RAID in Windows 7 that is called "Software RAID" and it will absolutely not allow you to dual boot (if it works on the system partition at all).
    – e40
    Commented Sep 20, 2011 at 14:40
  • I think I confused most of you here. I mean I am setting up the raid1 in BIOS. Now, booting into GParted, it shows me 3 things: the mapper, dev/sda and dev/sdb. If I want to make partition prior to installation, which one of the three should I choose to make the partition? I mean I am sure I can boot into Windows 7 installation, format the whole disk, and after installation make partitions... thanks e40. and again, I already have the raid1 setup already through BIOS. As I boot up the computer, it tells me RAID 1 is set for disk 1 and disk 2
    – CppLearner
    Commented Sep 20, 2011 at 16:35
  • my bad, i thought u were answering my new post superuser.com/questions/337259/…
    – CppLearner
    Commented Sep 20, 2011 at 17:06

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