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From: mjacob@wonky.Eng.Sun.COM (Matt Jacob)
Newsgroups: comp.periphs.scsi
Subject: Re: SCSI vs CAM (Was: SCSI driver source for SUN)
Message-ID: <7974@exodus.Eng.Sun.COM>
Date: 14 Feb 91 08:17:47 GMT
References: <487@lever.com> <3687@island.COM> <2063@atlas.tegra.COM>
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A few points:

	+ SCSA *is* available on non-SPARC sun machines (but not
as a bundled part of the OS. Grrr! Not my choice...).

	+ SCSA and CAM address a lot of the same issues. In all
fairness CAM goes a bit further than SCSA in defining ways
of allowing transport modules (host adapters drivers) to be plugged
into it. We are considering doing this for SCSA also, although
my take on this issue is that the population of target drivers
is 100s to one host adapter driver. On the other hand, SCSA is
a lot more lightweight than CAM (I imperfectly understand CAM
as yet, but it seems to me that performance issues was a non-goal
in the CAM effort- I am looking at the latest CAM specs in a couple
weeks so I'll have a better idea then). SCSA kept itself as
thin as possible in order to provide (in my opinion) a very
aware balance between the tradeoffs of portability/platform-independence
and speed.

	+ CAM hasn't got much field experience yet. That is, it
is in the process of final definition, but hasn't been out in the
field for a couple of years (as far as I know).

	+ SCSA's original goal was to unify a driver architecture
across all Sun platforms. It can be extended to non Sun machines
(nothing in the spec itself precludes this). The forum for doing
this is in the CAM process, as well as the IEEE P1256 OBIOS effort,
plus other areas.

-matt