Re: devfs
Michael Neuffer (neuffer@goofy.zdv.Uni-Mainz.de)
Sun, 11 Jan 1998 11:44:59 +0100 (MET)
On Sun, 11 Jan 1998, Richard Gooch wrote:
> > No not controllers. This is buses on the controller. 4 bits for this
> > should be the lower limit. The smallest SSA that you can buy from
> > SUN for example has already 6 buses.
>
> That's interesting. Since you seem to know something about SCSI host
> adapters with multiple SCSI buses, can you please tell us how they
> show that in /dev? I'm aware of the following format:
>
> cCtTdDsS
>
> where <C> is the controller number (host adaptor), <T> is the SCSI
> target (SCSI ID), <D> is the device number (LUN) and <S> is the stripe
> (partition).
>
> Where do they put the per-host/controller SCSI bus ID?
Solaris resorts to an ugly trick to encode the buses of the SSAs.
When speaking to an SSA the LUN gets dropped and the fields shift
right to make room for the channel (bus).
Now the meaning is follows:
cCtBdTsS
Where <C> is the controller, <B> is the bus/channel, <T> is the target and
<S> is the slice.
This allows then to stay compatible with their naming sheme but has the
drawback of dropping support for LUNs. This only works properly for the
special case of the SSAs since you only have disk drives in them.
However I do not think that we should make the same mistake as them
and cut ourselves off from supporting multi LUN devices.
Mike