Originally Posted by archangel_617b
What RAID controller did you have this problem with? All the RAID cards from Dell I've dealt with have been hardware RAID.
At my current job, all the computers are Dell and most of them are RAID, and so far as I understand, none of them are hardware RAID.
Some use motherboard "raid", some use Promise cards, some use some other brand of raid card. See my recent thread at
for one example with a Promise card.
Since I haven't used any hardware raid in many years (the last hardware raid I used was PATA not SATA), I'm curious about something:
If you boot up a liveCD (such as Mepis) without any special drivers for raid on a system with hardware raid, what drives do you see:
1) Doesn't work at all because you don't have the drivers?
2) The raid works anyway, because the raid controller makes the multiple SATA drives look like one SATA drive that the software can access without special drivers?
3) Each drive acts like an ordinary individual drive?
Obviously with fake raid it will be (3). Depending on how the fake raid is done, the MBR you see in that mode may or may not be the same sector as the MBR you see when the fake raid is active. So for raid1, you might see two identical drives or you might see garbage. (The Dell systems on which I've used Linux to help diagnose Windows problems have had both versions of that).
For hardware raid, with raid0 or raid1, what exactly does the hardware raid do? The software overhead for raid0 or raid1 is trivial (no XORs). It's hard to imagine what benefit hardware raid provides. I would expect software raid to make better decisions about command queuing and distributing the reads for raid1 than hardware raid could. (I know the Dell software for motherboard raid1 for Windows XP makes absurdly bad decisions about distributing the reads, but I'm hoping/assuming Linux software raid1 wasn't written by idiots).