Michael Grabenstein (mikeg@endgame.gsfc.nasa.gov) wrote:
: >In article <CM63wK.Bp1@twinsun.com> eggert@twinsun.com (Paul Eggert) writes:
: >>braida@cmc.ca (Gary Braida) writes:
: >>
: >>>Media Costs
: >>> 8mm $16 (112m data grade)
: >>> 4mm $27 (120m data grade)
Hmm. I was quoted ~$14 for 120m data grade 4mm tapes.
: > One thing here too is, that the 120M tape for 4mm is the longest
: >you can buy. The tape drives should accept 60M and 90M tapes too which are
: >cheaper. 90M tape stores 2 gig, 60M stores 1.3 gig, 120M I think is 2.7
: >gig, right? This is all without compression.
Well, 120m tape is not supported by DDS. DDS-2, however, does support it.
DDS-2 format is a little denser, so you get 4 GB per 120m tape without
compression.
: >>>Which one is faster
: >>That's true, but 8mm have about twice the transmission rate of 4mm at
: >>the same level of technology, which is not surprising given that
: >>they're twice as wide. For dumps, transmission rate is more important
: >>than seek time.
: >>
: > This is interesting, because my dumps to my 4mm tape drive have
: >always "felt" faster. But I have never really tested it (of course my 8mm
: >and 4mm are on different machines...).
It's possible that the 4mm is actually faster. If you've got a case where
the computer (or network) can't fill the 8mm buffer fast enough to keep the
tape streaming, then it has to stop and restart. This would slow it waaaay
down.
: > I am not up on the compression 4mm tape drives, but I know there is
: >an HP tape drive that can store up to 8gig, not sure on what tape. I assume
: >120M tapes.
The DDS-2 drive (4 GB native), assuming 120m tape and compression is
quoted at up to 16 GB. In real life, expect 6 GB worst case, and average
at about 8 or so. 16 is pretty unlikely.
--
Bill Wyatt, Smithsonian Astrophysical Observatory (Cambridge, MA, USA)
Internet: wyatt@cfa.harvard.edu BITNET: wyatt@cfa
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This archive was generated by hypermail 2.1.2 : Fri Sep 28 2001 - 23:08:57 CDT