Re: SAS scsibus target numbering

[Mouse <mouse%Rodents-Montreal.ORG@localhost>]

>>> it's usual for the SCSI HBA to assign a targetID for itself.
>> For real SCSI - ie, non-SAS - it's actually necessary; [...].  But
>> the host is usually ID 7.
> ISTR SPARC machines used an initiator address 6 for hysterical
> reasons.  I forget why.

That disagrees with my experience.  The SPARCs I've worked with put the
host at ID 7; when using SunOS, ID 6, if present, is usually expected
to be a CD drive.  (0, 1, 2, 3 were disk, 4 and 5 tape, and 6 CD, in
Sun's default config.)

On machines with OF (which includes most SPARCs I've seen), there
usually is an OF setting for which ID the host should use, but (again,
in my experience) the default is 7, and I'm not sure I've ever seen a
machine with it set to anything else.  Perhaps if someone were doing
clustering with SCSI as the transport...but I don't know if typical
SPARC SCSI interfaces are capable of being targets.

>> Perhaps this is a SAS difference?
> SAS doesn't use target IDs on the wire.  The "target ID" is something
> LSI came up with to provide backwards compatibilty with parallel
> SCSI.

"Compatability", feh.  If I can't plug existing drives and machines
into it, I don't consider it compatible, and indeed I consider calling
it SCSI at all to be deliberately misleading.  One of SCSI's major
strengths is its extreme compatability; except for the brief fling with
HVD, SCSI is pretty much "plug it in and it Just Works".  At least in
theory, and in my experience that theory is pretty close to practice.
I've heard people rant about how touchy SCSI is, but that hasn't been
how it's worked for me.  (Another of SCSI's strengths is its symmetry;
while I don't know enough to be sure, I expect SAS breaks that too.)

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