Re: SUMMARY: 8mm vs. 4mm

From: Paul Eggert (
Date: Fri Mar 04 1994 - 19:24:18 CST (Gary Braida) writes:

> Tape Drive Costs
> 8mm $3630
> 4mm $1650 (less than half the price of the 8mm)

Is the Canadian exchange rate that bad? You should be able to get
5 GB subsystem with compression, enclosure, cables, power supply, etc.,
for around US $2100.

>Media Costs
> 8mm $16 (112m data grade)
> 4mm $27 (120m data grade)

> * 8mm tapes are almost half the cost of 4mm tapes. We use Sony P6-120MP
> video grade tapes which we buy for $8 (CDN).

You can't use Sony P6-120MP video tapes in 8mm drives any more -- Sony
changed the formulation. You're better off these days with Fuji
P6-120MP DS, which you should be able to pick up for less than US $4,
depending on quantity.

>Which one is faster
> The only real concensus on this one is that 4mm drives seek much
> faster than 8mm drives.

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.

> If we crunch the drive and media costs to find where the breakover point
> is we'll find that if you plan to use a large number of tapes, more than
> 180, then its more cost effective to use 8mm.

The exact number of course depends on the costs. But I noticed that
your analysis neglected the fact that (again, at the same level of
technology) 8mm tapes hold twice what 4mm tapes hold, so you overstated
your 8mm cost per megabyte by a factor of 2. If you're a heavy user
(as opposed to someone who usually doesn't fill up the tape), this is
another advantage for 8mm.

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