Keld Jørn Simonsen wrote:
It is possible that I am thinking of what you call fakeraid.
I like "firmware raid" better, but the bottom line here is that the raid
is still done in the system CPU. These often have little or no hardware
support, such as cache so that multiple drives can be written without
passing the data through the system bus more than once (and chancing
change while that happens).
OK, if the definition on these controllers is that they must have support
from the OS, then I think most of the mobos today come with hardware
raid, that is there needs to be no support in Linux for this. Everything
is set up via the bios, and from the linux kernel it looks like an
ordinary disk.
The problem here is it looks like an ordinary disk to the BIOS only. Grub can use this to load the
kernel and initrd from, but when the kernel boots it sees the controller as the simple controller it
is with some disks connected to it. It requires something like dmraid to make the "array" visible as
an actual array.
None of these controllers perform any of the RAID offload themselves, it's all handled by the
driver. Windows loads using the BIOS and then hands over to the driver which handles the raid, just
the same as linux does with dmraid.
I believe some of the ITE chipsets can handle raid-1 and possibly raid-0 internally, and the kernel
has the ability to drive those as a raid controller, but they are somewhat rarer than the other
fakeraid implementations out there.
Brad
--
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