Newsgroups: comp.sys.dec
Path: utzoo!utgpu!news-server.csri.toronto.edu!helios.physics.utoronto.ca!ists!newshub.ccs.yorku.ca!brack
From: brack@agrajag.yorku.ca (Tony Brack)
Subject: Re: 8mm or 4mm?
Message-ID: <1991Jun25.181021.7508@newshub.ccs.yorku.ca>
Originator: brack@agrajag.yorku.ca
Sender: news@newshub.ccs.yorku.ca (USENET News System)
Organization: York University, Toronto, Canada
References:  <13753@mentor.cc.purdue.edu>
Date: Tue, 25 Jun 1991 18:10:21 GMT


In article <13753@mentor.cc.purdue.edu>, mckay@mace.cc.purdue.edu (Dwight D. Mckay) writes:
>> Our 8mm tape drive has once again died.  Twice in two years.
>> 
>> Since we are starting to handle a sizable amout of data created by the
>> X-ray instruments here, I'm considering adding a second drive.
>> 
>> Should I add another exabyte (8mm) or start switching over to DAT (4mm)?

This involves your own personal preference... We have both here, mainly
because we are concerned with being able to read from both media. The
down side of this is you would have 2 single points of failure. The plus
side is you can read/write both media types...

Don't expect TONS of better reliability with the 4mm drives. SONY's
have caused us grief on DEC/Mips offerings, largely due to ROM bugs
and the like. Archive drives seem to work rather flawlessly, and are
*much* cheaper... at least by our experience.

>> As I understand it the *big* differences are:
>> 
>> - Ignoring compression, 8mm has greater capacity then 4mm.
>> - 4mm is faster on "seeking" files
>> 
>> Suggestions?  Comments from owners of 4mm or 8mm drives?

8mm drives have capacities of 2.3 or 5 GB depending on whether or not
data compression is on, whereas DAT capacity is 1.2 & 2.0 GB respectively.
One interesting device we use which is relatively cheap is DILOG's DAT
stacker. It is about half-again the price of a SONY DAT, and allows you
to serially run through 8 cartridges. Again, the down side is the SONY
transport used internally. (No ROM problems on VAXen yet...ed)

If you'd like numbers, we have 5 stackers backing up about 10GB apiece
for full backups on weekends unattended.

>> BTW: This drive would be attached a VMS machine and used remotely via
>> Multinet from UNIX machines.

Let me know how & if you get this working! We tried and it didn't under
MultiNET V2.1. Too many problems with VMS unloading the tape drive after
rdump (rmt) exited. In particular it would be nice to pay attention to
tape labels, something VMS does poorly, but UNIX makes no attempt to do
in any way shape or form.. (a little stab here). Seriously, though, I
haven't checked if MultiNET 3.0 rmt is better documented than its
predecessor was... it may be worth giving another stab!

>> --Dwight D. McKay, Purdue University, Department of Biological Sciences
>> --Office: LILY B-145, Phone: (317) 494-4481
>> --mckay@gimli.bio.purdue.edu

-- 
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