%META:TOPICINFO{author="ChrisBartram" date="1147831059" format="1.1" version="1.1"}%
%META:TOPICPARENT{name="Hp3000DdsUnits"}%
<pre>
Short answer for the "cons":

   0) HP usually calls theirs DDS, sneering at the lowly DAT.  I think
      it's to distinguish the computer certified tapes from the
      audio tapes?

   1) DATs have no significant error recovery mechanism.

      If you encounter a tape error on a DAT, the rest of that file
      is inaccessible.  Subsequent files on the DAT might be accessible,
      if your software is smart enough to issue the appropriate
      "skip" commands PRIOR to encountering the bad tape area.

   2) DATs can't be read past the current end-of-tape marker.

      If you have a full DAT (say, 1.2 GB), and accidentally insert it
      into a drive (write enabled) and write over the first 2 bytes...
      poof! The entire rest of the data is "gone".  (For the *really*
      desperate, an unsupported desperation trick *might* suffice to
      get about 90% of the data back, with a lot of expensive work.)

   3) Lack of feedback

      You can't look at a DDS while in use, and estimate how much tape
      has been used.

      You can't determine how many write-retries were successfully done.

      (True, SCSIDDS offers a peek at both values, but with difficulty,
      and not all DDS drives on HP3000s are SCSI.)

   4) Slower per megabyte than reel-to-reel, I think.

   5) Slow load/eject times (compare to thread-it-yourself reel-to-reel,
      and to some auto-load reel-to-reel).

   6) Jamming in drive

Pros:

   1) capacity!

   2) small size!

   3) cheap!
</pre>

You'll note that none of the pros/cons are HP3000 oriented, but are true on any system. 

 --[[StanSieler]]

... we experienced consistently a fifty-percent wall-time reduction after switching from HP7980 reel-to-reel to the HP model 6400 4000 DC. That's the 120 meter variety with hardware compression. At first, we were continuing to have compression turned on in RoadRunner, but since we cannot turn off the hardware compression (5.0 push), it seemed redundant; we turned it off. The through-put improvement was a big surprise as the transfer rate is rated as significantly slower that 1/2" tape. No one can explain it, but it is not a fluke. 

 --[[LeonardBerkowitz]]

-- Main.ChrisBartram - 17 May 2006