TMF Reference Manual (G06.24+)

TMFCOM Tape Media Considerations
HP NonStop TMF Reference Manual—522418-002
4-5
Considering File Size Factors
Autoloaders help reduce the frequency of tape-handling by the operator and,
depending on the model, allow you to place six or seven tapes in the hopper at once.
The autoloader cycles through these tapes in order, loading them automatically.
Cartridge magazines allow you to transport and mount collective sets of tapes.
A Storage Technology Corporation (STK) Automated Cartridge System (ACS) reduces
the need for operator intervention more dramatically. For example, a single STK 4400
ACS holds up to 6000 tapes, and multiple ACSs can be configured on a single system
to provide even more capacity. An ACS can automatically mount a tape in less than 20
seconds.
Considering File Size Factors
Processing fewer large files typically produces a higher data transfer rate than
processing many small files. Operations with many small files involve additional
overhead per block; the system must open each file individually, ensure that it is
indeed the file requested, verify that it is available and that its security constraints do
not preclude access to it, and so forth. When a program processes small files, the
data transfer rate is lowered. With larger files, however, much greater rates are
possible.
The number of files, copied from disk, that a tape volume can hold is highly variable
and depends on two factors:
•
The capacity of the tape volume.
•
The average size of the files.
Some tape drives provide compression, some support 36-track recording, and some
offer both of these features. Be certain that the drives you use are compatible with one
another; otherwise, tapes written on one drive will not be readable on another. For
example, a compressed tape produced on a Model 5190 drive cannot be read on a
Model 5180 drive, which does not support compression.
For information about the characteristics and storage capacity of your tape drive, refer
to the manual for that particular drive.