Felipe Alvarez's blog

RAID – redundant array of inexpensive/independent disks

What a tricky little thing it is, especially the non-Hardware variety (i.e. a dedicated RAID controller card via PCI bus or PCI-e bus).

These are some of the things I think I know about RAID in GNU:

1. BIOS RAID (a.k.a. fakeRAID) is built onto motherboards to please Windows Users, because XP Home and XP Pro do not come with support for redundant arrays (RAID levels 1 and up). This means it only supports stripping (RAID 0). BIOS RAID is there to ‘save the day’ and support redundancy, as in RAID 1, 5, 1+0.
2. In GNU, one needn’t turn on BIOS RAID, one only needs dmraid (or mdamd), and more than one hard drive (only one is required, but more are highly recommended). All RAID levels are supported via Linux software RAID. The kernel has had lots of modifications over the years to very easily support RAID 0, 1, 3, 4, 5, 1+0.
3. dmraid (device-mapper raid) and mdadm (multiple-devices admin) are tools used to manage RAID arrays. I have not yet figured out the differences between them and which one I should use. openSUSE 10.3 has them both installed – adding lots of confusion.