SUMMARY: 8mm vs. 4mm

From: Gary Braida (
Date: Fri Mar 04 1994 - 09:38:42 CST

The following is a summary to my posting a few weeks back regarding 8mm versus
4mm tape storage devices. This summary is intended to be a general overview
of the comments I received.

Tape Drive Costs

   8mm $3630
   4mm $1650 (less than half the price of the 8mm)

   * 4mm drives are in general much cheaper than 8mm drives. The above
     numbers are real quotes for Sun tape drives.

     8mm drives are more expensive likely due to the fact that all 8mm drives
     are licensed by Exabyte. Therefore, resellers have to pay royalties
     which push up the cost of the drives. 4mm is an open specification
     which forces competition among other things but the net result is the
     same, better prices.

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). We have had problems in
     the past with some of the tapes but in general they have been very
     reliable. The above tape prices where taking from the INMAC (March 94)

Cost per Megabyte

   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. If you plan to user less
   than 180 tapes then 4mm drives are more cost effective. See below.

   Breakover Point:

      The breakover point is the point where the cost of buying 4mm and 8mm
      drives and media are the same.

        1650 + 27x = 3630 + 16x
               11x = 1980
                 x = 180 tapes


   Both 8mm and 4mm drives use heilcal scan technology.


   Judging by the ten or so responses I received most users feel that 4mm
   drives seem to be more reliable than 8mm ones. This isn't a large enough
   sample to make a real conclusion but I included it anyway. We have two
   2.3GB 8mm drives and one of them only works when it wants to.

Which one is faster

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

Protecting your investment

   One important issue is compatibility with your network environment. If
   you have a large install base of 8mm drives it may make more sense to
   continue with 8mm. On the other hand, if you don't have either a 4mm
   or 8mm drive then read on.


   It is really hard to predict how long computer hardware and peripherals
   will last in this day and age but most people felt that 4mm and 8mm
   technologies will be around for a few more years yet.


   Both 4mm and 8mm are viable solutions for magnetic media backups and
   both solutions are likely be around for a number of years.
   If you have a large install base of one or the other then you should take
   that into consideration when making a final decision. If you don't have
   a 4mm or 8mm drive but you would like to buy one then from what I can
   tell, most people would choose the 4mm. This is especially true if you
   only plan to use a small quantity of tapes (150-200).

   The general feeling was that if users had to go out and purchase either
   a 4mm or 8mm drive, most people would choose the 4mm.

   Given all the above information we have decided to purchase a 4mm
   DAT drive.

My appreciation to all those who responded!


Gary Braida | Canadian | ****** ******* ******
email: | Microelectronics | * * * * *
phone: (613) 545-2914 | Corporation | ****** * * ******

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