Xref: utzoo comp.periphs:1380 comp.sys.sequent:121 Path: utzoo!utgpu!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!mailrus!ames!pasteur!ucbvax!hplabs!nsc!voder!pyramid!csg From: csg@pyramid.pyramid.com (Carl S. Gutekunst) Newsgroups: comp.periphs,comp.sys.sequent Subject: Re: 2 Gb cartridge tape drive Message-ID: <51459@pyramid.pyramid.com> Date: 18 Dec 88 00:36:49 GMT References: <1180@fai.UUCP> <50451@pyramid.pyramid.com> <1261@fai.UUCP> <7378@ea.ecn.purdue.edu> <7546@ea.ecn.purdue.edu> Followup-To: comp.periphs Organization: Pyramid Technology Corp., Mountain View, CA Lines: 66 See George Goble's articles on Exabyte, which I have added to the references line. The drives Pyramid evaluated were made prior to June 1988, i.e., before Purdue and Exabyte ironed out some major problems. Much credit is due Purdue for working closely on Exabyte to solve their problems, as opposed to stone- throwers like me who just sit back and bitch. :-) Note that even the present drives do require the user to make a number of con- cessions. None of these would be a problem given the environment that Ron Christian described in his previous posting: periodic, overnight, unattended Level 0 backups. In article <1261@fai.UUCP> ronc@fai.fai.com (Ronald O. Christian) writes: [A lot of good reasons why the limitations of an 8mm drive don't cause any problems for his environment.] >> These are consumer quality, designed for use in Camcorders, with a low >> duty cycle. > >This makes sense. But the issue with us is monthly level 0 backups.... >Surely two tapes a month isn't too high a duty cycle? Of course not. But then you still need something else for incrementals. My point was simply that an 8mm drive alone doesn't necessarilly solve all your backup needs. But, as you observed, one can consider the drives disposable, relative to the very high cost of 9-track media. >>- Media integrity is *highly* dubious. > >It's true that data storage is another story. The data storage is digital >with error correction, whereas the camcorder signal is analog. One would >think that digital recording techniques would be more robust. All that digital means is that when the tape starts to deteriorate, you won't notice it for a while; the error correction will hide the deterioration. When the bit error count gets too high, whole 128Kbyte data groups will evaporate. >... The consensus was that 9 track tape is poorer quality than consumer video >tape, not the other way around. It's an apples and oranges comparison. 9-track tape needs to handle a bit den- sity of 112Kbits per square inch. 1/4" cartride using QIC-150 format, 600Kbits per square inch. For 8mm, we're talking 35 MILLION bits per square inch, and with DATs, a mind numbing 114Mbits. (For reference purposes, VHS digital is 13MBits.) The question of whether a 9-track tape can be used at high densities is not a quality issue, but a technology issue. There are manufacturers who are building 9-track, 1/4", and DAT drives and media to commercial/industrial specifications. No one is doing this for 8mm. And at 300 times the bit density, quality control is very important. >Is this all speculation, or do you have hard data to back it up? We have not done the kind of wear testing that the Purdue folks have, so what I know first-hand about tape wear is speculative. (What I saw about drive wear *is* first hand, but based on the Purdue results, somewhat dated.) We do have some hard data on tape wear characteristics, although the source is *ahem* somewhat biased: 3M Corp. :-) Please note that I am not flat-out rejecting the technology of helical scan 8mm (and smaller) tapes; I am asserting that what I have seen so far suggests that the technology is still immature. Much credit is due Purdue and Exabyte for their latest developments. But when Sony and Hewlett-Packard start to ship industrial-grade DAT drives early next year, I would guess that 8mm will prove to have been merely a transition technology.