Advice on change of tape drive please.

[Bill Codding]

In article <OPERATOR.90Nov20104952 at expya.cs.exeter.ac.uk> operator at cs.exeter.ac.uk (Sue Charles) writes:

   We at the moment have a QIC-11 tape drive on our sun and are backing up
   onto 3M DC300A -300ft Tapes
           DC300XL/P 450ft Tapes
           DC600A 600ft Tapes   using the maximum tape capacity.
   In the new year we will be installing a QIC-150 drive.
   Which (if any) of the above tapes would I still be able to use

If you want some really confusing, conflicting information on this
subject, call the 3M hotline.  Want to be more confused?  Call the 
drive manufacturer.

We had similar questions.  After what amounts to several
hours of experiments and being on the phone with the above goons,
the following information finally falls out.

1) Using our Archive 2150S QIC-150 drive (Stellar GS1000), we can 
   read AND write QIC-150, read ONLY QIC-24, and neither read NOR write
   QIC-11.

2) Our Sun-3 was able to write both QIC-11 (nrst0) and QIC-24 (nrst8).
   Only the higher density is readable in the QIC-150 drive.  I believe 
   Sun-2's only wrote QIC-11.

3) 3M said you should not use more than one type of tape in a drive,
   as the heads "wear in" to one type; using another can cause reliability
   problems.

  a) 3M explicitly said to not combine DC600A's and DC300XL/P's
  on one drive.  Upon pressing them for details, however, the two seem
  to be the same form factor, same thickness vinyl, just a different
  coating/oersted rating.  I find it hard to believe you cant mix
  different _coatings_ in your drive....  Archive says it is OK to
  read the occasional DC300XL/P in your QIC-150 drive, though.

  b) Archive says you can use either DC600A or DC6150 on their QIC-150.
  They say the physical medium is the same, so no wear problems.  However,
  the 6150 has an additional capstan (roller) and a wider opening in the
  plastic housing.  The tape identification marks tell the tape drive
  to write more tracks on the 6150, since the housing hole allows more head
  clearance.  Thus, 120MB on a 600A, and 150MB on a 6150.

  c) The 6150 is actually Archive's recommended tape for the QIC-150; the
  600A was originally designed for a lower capacity drive (hence the "60MB"
  marking on the case) but will work writing fewer tracks.

  d) Archive says you cannot interchange [DC6150/DC600A] and the DC6250.
  The 6250 is thinner tape, and causes the head to wear more (or less??)
  convex-ly.

4) 3M sometimes gives different MB ratings to tapes which have the same form
factor, coating, thickness, etc; the only difference being that they
are marketed for use on drives which write different numbers of tracks!

Whatta waste of brain space.  This isn't even my job.
I'm charging them $10,000,000 for my time.

------------------------------------------------------------------------
  Bill Codding                                       (415)493-3554 (w)
  Research Engineer                                  (415)751-5484 (h)
  P.E.D.A.                                peda at simplicity.Stanford.EDU
------------------------------------------------------------------------