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From: thad@cup.portal.com (Thad P Floryan)
Newsgroups: comp.sys.amiga.hardware
Subject: Re: Who's got the biggest SCSI drive actually functioning
Message-ID: <31485@cup.portal.com>
Date: 6 Jul 90 09:05:42 GMT
References: <1990Jul4.035345.18031@zorch.SF-Bay.ORG>
Organization: The Portal System (TM)
Lines: 87

xanthian@zorch.SF-Bay.ORG (Kent Paul Dolan)
<1990Jul4.035345.18031@zorch.SF-Bay.ORG> asks questions concerning large
capacity HDs.  Here are some answers based on my setups and experiences
using a Supra 4x4 on several A1000 systems (also equipped with Ronin stuff):

	1) What's the biggest SCSI drive anyone has up and running, say
	   for at least a couple of months to make sure it's stable?

The very large Maxtors work fine and reliably.  I even used one of their
1+ GB drives for a week which was the max I could get it on loan.

	2) Does the software Commodore supplies with 1.3 suffice to
	   low/high level format such a beast, or does the vendor have
	   to know enough about the Amiga to supply some software to
	   do the job -- i.e., can I just buy hardware?

Perhaps.  Considering the problems with which I helped Dale Luck attempt to
setup a Maxtor XT3380 on an A2090 on one of his A2000, we never got it to
work.  The same drives work fine on my setup.  (Dale's problem was about 18
months ago, and perhaps it's been fixed since, but I don't know.)

	3) Are there limitations in AmigaDOS or in the SCSI standard that
	   force large disks to be partitioned in multiple pieces, or can
	   I just make it one huge tree?

I abhor disk partitions.  The only OS that is accursed with the requirement
for partitions is MS-DOS, and even their latest version(s) have removed that
barrier.  But, then, I often need to work with >100MB data files and I prefer
dynamic demand resource sharing of ALL system resources (which is but another
reason I detest VAX/VMS with its quotas, limits, barriers, fences, etc.)

SCSI commands are essentially "by block." I.e. you ask the drive for block
123, you get block 123.  You write block 12345 and the drive writes what you
present to it.  The I/O commands are not cognizant of drive geometry.  I don't
understand why (most) SCSI support packages for the Amiga insist on being
given the number of heads, cylinders, etc. when the software "should" simply
interrogate the drive and find out for itself whatever it needs; in fact all
it needs is the drive's capacity, PERIOD (e.g. the max number of sectors of
which the device is capable).  This is one of the attractive aspects of SCSI
(on "other" systems :-)  Modern SCSI HDs even alter their geometries based on
the radius (~ cylinder) in attempts to maximize capacity in smaller packages.

	4) If I can make it one big partition, are there good reasons for
	   making it several smaller ones instead?

Considering the difficulty getting tape drives working for ALL Amiga setups,
my advice re: partitioning is to partition ONLY if you cannot afford to nurse
an all-files backup in one sitting.  The last all-files backup on one of my
Amigas required 1,604 floppies using Quarterback.  I'm testing some tape
software on and off recently and have 5 different tape drives being tested.
Seems the problem(s) center(s) around SCSI-direct commands.

	5) Has anybody got experience with a streaming tape backup that
	   runs on the Amiga and can back this sucker up on one tape?
	   Vendor, prices, software used/needed?

See answer to (4).

	6) Rewritable video disk technology is available for the Amiga
	   now, but the storage (per diskette) is no greater than this
	   magnetic drive, and the best price I've seen for the video
	   disk is around $9K, a bit steep for an unemployable graphics
	   [ ... material deleted ... ]

A SONY DAT SCSI tape backup unit was shown at last month's FAUG meeting.
It's not yet functioning on the Amiga.  The cartridge is barely larger than
three credit-cards placed atop one another and stores 1.2GB (yes, gigabytes).
The unit DOES work fine on an "IBM-PC" with an Adaptec 1542 SCSI card.

Kinda weird how SCSI has come so late to the ``PC'' marketplace yet the
overall SCSI support is so much better for the ``PC'' than for other systems.
Some of the freely-redistributable software from one of Adaptec's field
service persons in Texas even allows one to alter the SCSI OS in SCSI devices.
Great stuff!  Now WHY isn't such good software available for the Amiga? 

	7) Is the $2500 price for the magnetic disk I'm being quoted a "good
	   deal"?  ;-)

That price is not unreasonable for a single 600+ MB HD (assuming it's new).
Just be SURE you get a good "shoebox" case with hefty power supply and good
cooling fan for it.  Those large HDs require a LOT of startup current and
most power supplies will just cog the drive and not start it spinning up.
Generally speaking, the line of Astec (not a typo) power supplies are the
ones recommended for use with Maxtors (and are the ones found in the Storage
Dimensions (a Maxtor subsidiary) SCSI HD subsystems last time I checked).

Thad Floryan [ thad@cup.portal.com (OR) ..!sun!portal!cup.portal.com!thad ]