Booting from firmware RAID

b. f. bf1783 at
Wed Mar 16 14:11:49 UTC 2011

> This is probably more PC-specific than freebsd-specific question. I have
> intel firmware raid. OS needs drivers to work with it. FreeBSD sees it as
> ar0, so it has drivers.
> But I want my OS to be installed on this drive and boot from it. It is not
> good idea, but I really want to do it:)
> Is it possible?
> boot0 and boot1 both work with HDD via BIOS interrupts and CHS, right? So,
> how do they know how to access RAID? They has no drivers.
> Or BIOS supports interrupts to access RAID with out of drivers? If so --
> what for drivers are needed? To access drive via ATA interface?
> Is it possible to boot freebsd from "firmware raid"?

Sometimes: it depends on the firmware, and your bios.  I had a add-in
PCIe SATA RAID controller based on a Marvell SE9128 chipset, and using
a Marvell firmware.  The bios and the FreeBSD 9-CURRENT bootloader
were able to boot from a JBOD drive attached to the controller, up
until the point where the ahci driver tried to take control of the
drive.  Then the Marvell firmware presented a fictitious configuration
to the ahci driver and returned invalid device signatures, so the boot
process failed.  On the same machine, however, I was able to boot
without problems from a JBOD drive attached to a PCI-X SATA RAID
controller based on the Silicon Image SiI3124 chipset, using a Silicon
Image firmware.


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