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turer claims that, on average, this unit will run for 10,000 hours (or
about 416 days) before it will break down and stop working. The bot-
tom line is this: the DLTtape system, with its patented head design, low-
tension-tape contact, simple tape path, and stationery heads, has an
inherently more reliable design than that of competitive products.
Reliability and Environment
Another spec to look at when you compare reliability is environmen-
tal operating conditions. MTBF is calculated based on a formula that
takes into consideration multiple factors for all the parts of the prod-
uct and statistically merges them. Heat is the single greatest enemy of
reliability. So one very simple way to increase calculated MTBF is to
narrow the temperature range across which the product is assumed to
be running. If you assume the unit will always operate in a 70°F room,
you get a lot better figure than if you say it might have to function in a
100°F room. Our MTBF calculations for the DLTtape drives are based
on a temperature range of 50°F to 104°F (10°C to 40°C), a wide range
that reflects the worst conditions the system is likely to encounter.
Head Life
The read/write heads are among the most wear-sensitive and
expensive parts of the tape drive. Obviously, they are an important
factor in overall unit reliability. Head life for DLTtape drives is also
calculated in a fashion similar to MTBF for overall drive reliability
(i.e.,under severe temperature and humidity conditions). The
numbers would be even more impressive if we calculated for a typ-
ical office environment. Because head life is a critical reliability
measure, we are extremely conservative in making our calculation.
Durability: Tape Passes
Media durability is measured in tape passes. How many times can the
tape be run through the unit before it wears out? The figure we use for
the Quantum DLTtape media is 1,000,000 passes. However, you should
not compare that figure directly against competitive drives, which usu-
QUANTUM DLTtape HANDBOOK
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