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From: baldwin@usceast.UUCP (Chuck Baldwin)
Newsgroups: comp.periphs,comp.sys.dec
Subject: RE: Helical-Scan Query
Message-ID: <2648@usceast.UUCP>
Date: 13 Jun 88 21:24:13 GMT
Lines: 60


Hi All:

     Several weeks ago, I posted a request to the net for information
concerning Helical-Scan backup devices.  Of the five, count'em 5, responses
I received three were requests for a summary of the information I obtained.
Well, as you can guess, there aren't many in use. The only reply from
someone with a Helical-Scan backup device in use follows:

> We got our "Exabyte 8mm Tape Drive Subsystem" for our Sun from 
>Perfect Byte, Inc, 7121 Cass Street, Omaha, Nebraska 68132, 402-
>554-1122.  Keith Wagner is the president (ihnp4!pbi!keith). The 
>unit came with the Exabyte 8200 drive, a Ciprico 3500 controller,
>cables, and software.  It was easy to install and preforms the 
>standard Unix tape i/o just fine. 'Tar', 'dd', 'dump/restore' have
>all been tested and found to work. I can 'dump' at about 10Mb per
>minute to the drive. Should be able to 'dump' at least 4 Eagle XPs
>to one tape. Tapes cost about $8 each.
                      .
                      .
                      .
>        bull@noao.arizona.edu
>        Frank Bull
>        Cadet Commander, Solar Patrol (Sun Systems Administrator ;-)
>        Central Computer Services
>        National Optical Astronomy Observatories
                      .
                      .
                      .

     The following reply, from David Lesher, has created a lot of rethinking
about the entire problem:

>I am very wary of such devices. Since there is NO way to
>verify (read after write) on a vcr [besides stopping the tape,
>going back to the beginning, reading and comparing, etc]
>the ones I have seen record each file several times in hope
>that one is perfect. 
>Do you want to risk YOUR data to such a bet?
>On the other hand, the WORMS I have seen look nice.

     For those who don't know, WORMS, stands for Write Once Read Many.  The
most readly seen WORM is a laser disk, i.e. CD player.  These storage devices
store HUGE amounts of data, but only once.  This may be useful for system
backups, or possibly everyday backups depending on how much data is being
stored.  Also, I have been reading comp.sys.sun and the SunSpots literature
about 8mm Helical-Scan devices on Suns; and there is some discussion of the
various error recovery schemes in the devices.  Anyway, we're examining the
cost effectiveness and error recovery inherent in this solution.

     Considering the response we have received we're still not going to make a
purchase soon.  In the mean time we are going to keep on worrying with 2400'
tape.  Thanks again for all the help and if anyone gets one of these devices
please drop me a note about your experiences.

                                                   Chuck Baldwin
-- 
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UUCP: ...seismo!ncr-sd!ncrcae!usceast!baldwin	CSNET: baldwin@cs.scarolina.edu
Chuck Baldwin, Dept of Math, University of South Carolina, Columbia, SC 29208
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