Re: AHCI should try to claim all AHCI controllers

[Mark Lord]

Alan Cox wrote:
> Ar Maw, 2006-10-31 am 21:22 -0800, ysgrifennodd Linus Torvalds:
> > (We had the same issue with "PCI IDE controller". Some PCI IDE controllers 
> > are clearly exactly that from a programming interface standpoint, but 
> > because they support RAID in hardware, they claim to be RAID controllers, 
> > since that is more "glamorous". Gaah ;^).
>
> Actually its far uglier than that. With one exception they don't support
> hardware raid mode, they use the RAID class tag to stop other OS drivers
> grabbing the interface or seeing it directly as un-raided software raid.

Note that a lot of the software raid controllers actually have full
hardware RAID acceleration in the chipset (single block command is automatically
remapped across several drives of a RAID 0/1/10 configuration, reducing bus
transactions and bandwidth requirements.

But they still require a driver do perform the RAID management,
and are thus not true "hardware" RAID.  But they are higher on the
food chain than total "pretend" RAID devices.

Cheers
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