From: dtb@adpgate.UUCP (Tom Beach)
Newsgroups: comp.periphs
Subject: Re: DAT users ?
Date: 6 Apr 92 15:22:19 GMT
Organization: ADP Dealer Services R&D, Portland, OR

daveg@prowler.clearpoint.com (Dave Goldblatt) writes:
: On 2 Apr 92 16:09:40 GMT, dtb@adpgate.UUCP (Tom Beach) said:
: 
: TB> If you're highly concerned about capacity there's a good chance,
: TB> particularily in the PC world, that you're using some sort of disk
: TB> compression, Stacker, ..... That being true, DAT data compression
: TB> is a total waste of money!!!! Compressing data which has already
: TB> been compressed once only takes time, it doesn't double either speed
: TB> or capacity. In fact, if I remember the HP compression algorithm
: TB> properly, when the compression software senses "compressed" data
: TB> it simply stores it making no attempt to do further processing.
: 
: You're making a strange assumption here -- that you're going to do an
: image backup of your hard disk onto the tape.  I don't know ANYONE on
: a PC who does this.

Nor do I. You just demonstrated how incomplete my knowledge of how stacker
works is :-( Thanks for the information! 

: For those who aren't familiar how Stacker, etc. work, they basically
: allocate most of your PC's hard disk into a single file, then turn
: that file into a virtual drive, compressing and decompressing data as
: it moves in and out of the "drive".
: 
: When you go to backup your compressed patition, you're going to do it
: on a file-by-file basis.  As such, it will be decompressed as it's
: passed to the backup software, pumped out over the SCSI bus, and
: compressed as it's written out to the drive.
: 
: TB> The fact is that 8mm tape has more than double the area of DAT tape.
: TB> The technologies are comparable. Given that, 8mm will **ALWAYS** win
: TB> in capacity. If you're highly concerned about capacity, buy an 8mm!!
: TB> If 2 GB is satisfactory for your present and projected needs and you
: TB> like DATs small form factor and enhanced features then buy DAT, but
: TB> don't buy this "If you really need capacity buy a DAT with data
: TB> compression" nonsense.
: 
: Obviously, you're speaking from experience.  With what, I don't know.

 
With 2 yrs of 8mm experience on multiple platforms and fairly extensive
testing of several DAT products.
: Now, buying an Exabyte with compression is equally "nonsense"?

YEP! In comparing the technologies I only worry abofut uncompressed data
capacity. Like I said before, anything you can do in one, you can do in
the other. 


: From what I've seen in the lab here, the only thing faster than the
: DAT (HP's 35480A - yes, with compression {Hi Kevin!}), is a 3480.  The
: 8mms are _slow_.  Besides, 9-track has a greater physical area than
: 8mm.. ;-)

Compare it to an 8500 with compression. And use a large enough data
file so the the the 8mm's admittedly absurdly long start up time doesn't
overwhelm the data transfer time.

If you're making small backups, e.g. < several hundred MBytes 8mm
won't fair well. You're right about 1/2 tape, by the way. Look how
much data they get on VHS tapes :-)

: I also tend to believe the DATs are more reliable than 8mm.

Judgement call, I won't argue!
 
: {standard disclaimer: These are my opinions only.  Clearpoint may
: or may not share them; they're certainly not paying me for 'em!}
: 
: -dg-
: --
: "President Bush, do you think we'll    |  Dave Goldblatt [daveg@clearpoint.com]
:  have to go to war with Iraq if they   |  Subsystems Engineering
:  continue to defy the U.N.?"           |  Clearpoint Research Corporation
: "Oh, God, I hope so."                  |  Hopkinton, MA 01748 - (508) 435-7425
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