Drives are susceptible to damage from heat, in-rush currents, random
death of microcircuits, and field decay.
1. At all times, everything in the universe is decaying at some rate,
possibly a very fast one (ripe peaches in a warm dark place) or very
slowly (oxidation of properly anodized aluminum in a cool dry place).
The vast majority of these processes are accelerated by heat, most of
them double with every 10 centigrade* degree increase in temperature.
Room temp is 20, most electronics routinely operate at 40 or 50.
Failures here are proportional to temperature delta and time activated.
2. When a circuit is activated there is always an inrush current that
exceeds the normal operating current. The most common example of this is
tungsten lamps, because the electrical resistance of cold tungsten is
much lower than hot tungsten the initial current through a 60 watt bulb
might be well over 600 watts, but only for a microsecond. (600 watts
will heat up that filament that fast.) Any weakness resulting from the
first cause will be exposed when power is applied. This is largely a
matter of the incredibly tiny wires connecting the outside of the
visible chip package to the actual surface of the chip, wires much finer
than a human hair. The fewer times you turn them on, the less often
those things will fail.
3. Micro circuitry depends on a certain amount of magic. There are
cosmic rays whipping through, and just like they used to fog our slowest
film in the freezer, they can bump a few electrons around in a crucial
chip in a drive controller. These errors are proportional to the time
since manufacturing, regardless of whether the power is on or not.
4. Magnetic media depend on using electrical signals to create magnetic
fields which change the magnetic orientation of a material susceptible
to those changes. As the density of information increases, the size of
these fields dramatically shrinks, and the strength has to as well or it
would corrupt the area around it. Susceptible material may hold your
data, but it really wants to either align with the magnetic field of the
planet or to become totally random. Don't look now, but if you still had
8" floppy drives, you'd probably find that many of your 8" floppies are
no longer readable. Because a disk in operation is constantly checked
and renewed by the operating system, these errors are proportional to
the length of time the disk is shut down.
So, if your drives are properly cooled, keeping them spinning eliminates
#2 and #4. I store all my data on mirrored drives that are running
unless the mains power fails for over an hour, and backup to hard drives
that are only on during backups, or are on one week at a stretch and
rotated offsite for alternate weeks. Getting a copy offsite prevents #1,
operator error, and catastrophic losses such as lightning strikes and
building fires. The combination is pretty good.
Van
* Celsius is a centigrade scale, so is Kelvin, feel free to make up your
own. The numbers aren't important, just the size of the degrees. Room
temp won't be 20 in other scales, but the delta between ambient and the
operating surface of the chips will be the same.
On 26/11/2010 8:55 AM, Sue Daniels wrote:
>
> Larry - I keep my external hard drives on all the time. Have you
> found, if you
> only turn on when needed, that they are less susceptible to crashing?
>
> Sue Daniels Photography
> www.suedanielsphotography.com
> 303-258-0266
>
> Catch my work on Facebook: facebook.com/suedanielsphotos
>
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