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From: John Capo <jc@irbs.com>
Message-Id: <199512130018.TAA20346@irbs.irbs.com>
Subject: Re: SCSI vs EIDE
To: ctassell@isn.net
Date: Tue, 12 Dec 1995 19:18:29 -0500 (EST)
Cc: freebsd-isp@FreeBSD.ORG
In-Reply-To: <199512121028.GAA15284@phoenix.isn.net> from "Charles Tassell" at Dec 12, 95 05:10:59 am
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Charles Tassell writes:
> 
>   I'm setting up an ISP for a guy who REALLY wants to use EIDE 4 drives
> (transfer rate around 12 meg/s I think he said)  Now considering the fact that
> all PCI boards come with build in EIDE controllers in them, why is everyone so
> big on SCSI?
> 
>   I'd personally rather use SCSI myself, just because I have doubts as to
> whether or not EIDE is really as stable as they say, but I may be outvoted in
> this.  Can anyone out there come up with some convincing arguments why to go
> SCSI?  BTW: The machine is going to be an all-in one server: news, mail, WWW,
> DNS, terminal server (yey!  this wont crash often <S>)  And, we might run BSD
> instead of FreeBSD.
> 

I am not at all familiar with EIDE.  Perhaps it has some of these
SCSI features.

1) Overlapped I/O. I/O requests outstanding on all targets at the
    the same time.

2) BUS mastering DMA.  Minimal computes needed to move the bits.

3) 7 disks/tapes per bus.

4) Trivial to add large capacity DAT drives.

5) Automatic bad sector remapping.

6) Tagged queueing.  Multiple I/O requests outstanding to each target.

7) Wide SCSI is really fast.

8) Better support for SCSI in most if not all *nixes.

If they insist on one machine, make sure it has /plenty/ of memory.


John Capo                                                   jc@irbs.com
IRBS Engineering                       High performance FreeBSD systems
(305) 792-9551                 Unix/Internet Consulting - ISP Solutions