On Thu, 24 Apr 2003, Jon LaBadie wrote:

> In the charts presented at the talk I was struck by the relationship between
> tape capacity and data rate.  Assuming the maximum capacity tapes for the
> format, the data rate always seemed to be 1/10000th of the capacity (a small
> fudge factor is needed).
>
> For example, a Super DLT-220 has 110GB capacity, 11MB data rate.
> An Ultrium 1 with 100GB capacity has 10MB data rate (7.5 - 15 depending on 
> manufac).
> A DDS-3 with 12GB has 1.0MB rate and a 5GB 8mm tape has a 0.5MB rate.
>
> An upshot of this is that no matter what format, writting a complete tape
> takes approximately 10000 seconds, nearly 3 hours.  The technology 
> improvements
> have not improved the time it takes to write a tape.  Just how much you write
> in that time.

Hmm...  I remember discussing this very metric with our vendor
several years ago, but this is not the conclusion we reached.

Some counter-examples:

DLT4000  20 GB    5.4 GB/h   ~4 hours
DLT7000  35 GB   18.0 GB/h   ~2 hours
DLT8000  40 GB   21.6 GB/h   ~2 hours

Ok.  Those aren't so far off, and the rest seem remarkably consistent
with the ~3 hour metric.

-Mitch