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On 20/01/2006, at 11:18 AM, David Rhodus wrote:
> Is there a reason one couldn't just port the driver from FreeBSD ?

The freebsd driver has nothing in it to help us towards bioctl
support for 3ware controllers.

bio is all about having a single tool in userland to manage a diverse
set of RAID controllers, with the smarts for dealing with the
different controllers in the kernel driver. This can be compared to
using ifconfig to manage and control the huge number of different
network interfaces that are out there. ifconfig issues a generic
request to the kernel and the driver deals with making it happen for
that particular card.

The freebsd idea of support for a raid controller is to open up a
massive hole for a (vendor supplied and closed binary) userland tool
to talk directly to the hardware with. The kernel is dumb and just
passes messages around. To continue the comparison to ifconfig, if
you took this approach to configuring your network card you would
need to install a binary from the manufacturer of your network card
and use that to change the ip address on your interface. For added
fun the ifconfig tool from each vendor would work differently to each
other and they would all have different terminology for the same things.

bioctl is the ifconfig of raid controllers. The whole point of it is
to provide an abstract interface on top of your hardware. This
approach of abstracting things obviously works well for network cards
and I see no reason for RAID to be any different. Can someone please
explain to me what is so special about a RAID controller that
prevents us from doing it? Why should we support these binary tools
when they're the wrong way to do this?

dlg