Jon said.

> for both 2400 and 3600 foot.  The records are 380 bytes and the blocking
is
> under my control.  We use the Mag Drive for a very low volume so I'm not
> sure I am concerned about the wear factor.

Jon -

Back in the 1600 bpi days, the Inter-Record-Gap (IRG) was .75". If you do
the calculation of at 6250bpi with a 380 byte record, at one record to
block, you come up with the following calculation.

380 bytes * 9 = 3420 bits  / 6250bpi = .5472"

5472" + IRG (.75") = 1.2972" per record/block

2400/feet * 12" / 1.2972" = 22,200 records per 2400' tape.

3600/feet * 12" / 1.2972 =  33,300 records per 3600' tape.

at blocking factor of 10, the calculations are:

5472" * 10 = 5.472 + IRG (.75") =  6.222" per 10 records/block

2400/feet * 12" / 6.222" = 4,628 blocks per 2400' tape (46,287 records)

3600/feet * 12" / 6.222" = 6,943 blocks per 3600' tape (69,431 records)

I am not sure if the IRG is still .75".

My suggestion is to write 10, 20, and 30 thousand records to the tape with
a blocking factor of 1 and see how far the tape gets.  From that, you can
see how close the calculations are.

And of course, Your Mileage May Vary since my calculations are 90% therory
and 10% old memories.

/alan
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