Devices numbering [Was Re: Switch from legacy ata(4) to CAM-based ATA]

Garrett Cooper yanegomi at
Thu Apr 21 22:24:01 UTC 2011

On Apr 21, 2011, at 10:48 AM, Arnaud Lacombe <lacombar at> wrote:

> Hi,
> On Thu, Apr 21, 2011 at 1:31 PM, Garrett Cooper <yanegomi at> wrote:
>> Although this may not be a list of fixable issues, here are some observations (in part with the new geom raid infrastructure):
>> 1. Channels are no longer fixed of course because ata uses cam now, and I believe that device numbering is done based on probe ordering. This is fun to work with when dealing with appliances or configurations that require deterministic probe and mount, especially when drives fail, go missing, etc, but can be hacked around in device.hints. This is why it would be nice for geom labels to work in a sane manner.
> Out of context, but the same issue appear with network interfaces. If
> you're got 6 networks interface and the 3rd chip die, the 3 last get a
> bad numbering. I am not sure it is fixable by any device.hints.
> The Linux' world has the same issue (well, worse actually, as all
> interfaces uses the same 'eth' name). RedHat has been/will be
> introducing "Consistent Network Device Naming"[0,1] in Fedora 15,
> which may be an interesting move.

I'll have to look at this more in-depth, but this could be promising -- depending on how portable the biosdevhelper tool is.


PS while we may have a similar problem, at least the BSD interface names are more sane than the Linux ones. Overall it would be nice to alias multiple logical names like "management", "data", etc, like we may present to customers, but I don't know if someone has come up with an intelligent way to map out system topologies yet. It would be nice if serial numbers were exposed using a vendor independent mechanism. 

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