Re: Switchover to CAM ATA?

On Mon, Apr 26, 2010 at 12:19:46PM -0600, M. Warner Losh wrote:
> In message: <20100426181209.GB3012_at_garage.freebsd.pl>
>             Pawel Jakub Dawidek <pjd_at_FreeBSD.org> writes:
> : On Mon, Apr 26, 2010 at 10:33:27AM -0600, M. Warner Losh wrote:
> : > I've read most of this thread.  I think this is cool technology.
> : > However, before we move forward with this, we need to have a plan for
> : > the various issues that have come up.  The plan needs to be specific,
> : > have owners for key items, warnings about ownerless == obsoleted, and
> : > target dates.
> : > 
> : > I think this is one of the cases where we should record the plan of
> : > record on a wiki.  It worked well for other times we've had big,
> : > disruptive changes.
> : > 
> : > My opinion for the path forward:
> : > (1) Send a big heads up about the future of ataraid(5).  It will be
> : >     shot in the head soon, to be replaced be a bunch of geom classes
> : >     for each different container format.  At least that seems to be
> : >     the rough consensus I've seen so far.  We need worker bees to do
> : >     many of these classes, although much can be mined from the ataraid
> : >     code today.
> : 
> : This shouldn't be a bunch of GEOM classes. This should one class which
> : recognize multiple formats, just like the LABEL class.
> : I don't think it is feasible to reuse gmirror for that, it wasn't
> : designed in something like this in mind.
> 
> OK.  Maybe I got the consensus wrong...  My key point is that we need
> a plan moving forward, we need to identify what's actively being
> worked on vs "somebody else[tm] should do tihs" and when it needs to
> be done "or else".

You most likely got it right, I'm just saying creating separate GEOM
class for each metadata format is wrong direction. :)

> : > (5) Issues with glabel and ataraid(5) need an owner, and need to be
> : >     resolved, since the device names here are likely to change.
> : 
> : What are the issues?
> 
> ataraid doesn't remove the underlying ad* devices, so glabel often
> picks those up instead of the ataraid device, and you only get 1
> disk's worth of raid device...  So no mirroring or only 1/2 a striped
> volume.

It not only leave ad* devices, it doesn't even open them properly using
GEOM. It's internal ATA hack, which is PITA.

-- 
Pawel Jakub Dawidek                       http://www.wheelsystems.com
pjd_at_FreeBSD.org                           http://www.FreeBSD.org
FreeBSD committer                         Am I Evil? Yes, I Am!