AHCI, RAID and 7... is this normal?

saverio · 26 Aug 2009

Hi all,

My current 7100 RC installation sits on two hdd's in RAID 0, provided by the onboard controller; in this case an Intel IHC10R.

I switched the disc mode in BIOS to AHCI; the intent was to reformat and re-install a BSD based system on the second drive, 7 back on the first, and dual boot.

Now, here's the interesting part, I missed the boot prompt and it went into loading windows again, however, it loaded straight into Windows 7.

So although I took the boot order off raid and selected AHCI, it still boots fine!

I don't really understand what went on, but i'd love to know, so I'd like to ask you guys if you can shed any light on this. :)

XGUNTHERC · 26 Aug 2009

you're on your own with that one, maybe someone else can answer that one. I don't know why it's still booting after that. lol

ThymeJ · 27 Aug 2009

My guess as to why you can still boot your HDD was your RAID 0 was not really striping the two HDD's (using both HDD's at he same time for better throughbut). It was just making the two HDD's look like 1 HDD to Windows. It used HDD 1 first, and since you never filled it up, it never needed to use HDD2. Or maybe your RAID 0 was really RAID 1 (mirrored) and you did not notice it.

My $0.02.

BTW, does the Win7 now show your HDD as half the size it was when it was in RAID 0?

Dwarf · 27 Aug 2009

My guess would be that you didn't actually have it set up for RAID in the first place. You probably had it set up as a JBOD array. Although this is set up through the RAID configuration, this is as far as it goes. It is not true RAID where you have striping and/or mirroring between the disks. Rather, JBOD allows your system to have a single drive composed of 2 or more individual drives. The total size of this drive is the sum total of all drives in this array. Providing that the amount of data stored does not exceed the capacity of the first disk in this array, you can break it (as you have done) and not notice any difference with it, other than the reduced total capacity.

saverio · 27 Aug 2009

That's very interesting, thanks guys. ISo even though the the onboard software raid controller was telling me that it was Raid 0, and got me to select the stripe size et al, it was in effect just letting me see the two discs as one volume. That makes alot of sense.

I suppose this also answers why separate controllers from the likes of adaptec are always a better proposition.

I think for me the most interesting aspect of this, and with your replies is that I've been convincing myself that the system is faster etc. etc. and in reality having it all on one disc would have made no difference to speed.... which is further proof of how quick 7 is out of the box.

swarfega · 27 Aug 2009

Did you actually press ctrll+I during boot to get into the raid setup and create an array?

saverio · 27 Aug 2009

Oh definitely, set the member discs up, select stripe size, and then in the bios proper set sata configuration to RAID as opposed to ahci or ide !!