Kate wrote:
>
> "Brian A." <gonefish'n@afarawaylake> wrote in message
> news:%23eytoGNQIHA.4712@TK2MSFTNGP04.phx.gbl...
>> "Kate" <@*slamaspam*.demon.co.uk> wrote in message
>> news:OeMlF%23MQIHA.3532@TK2MSFTNGP04.phx.gbl...
>>> I recently purchased my first external HD. Can anyone tell me how
>>> long the data will survive intact once the drive is unplugged from
>>> the electricity supply, or is this something that varies depending
>>> on model and make, please?
>>>
>>> Many thanks
>>> Kate
>>
>> Disconnecting the power is not a factor of data
>> corruption/degradation unless it's not disconnected properly. Where
>> and how the disconnected drive is stored is a factor which depends
>> on room temp, moisture, objects near it, etc. When stored properly
>> it could last anywhere between shortly after disconnecting it up to
>> approx 10yrs depending on the integrity of the drive.
>>
>> Brian A. Sesko { MS MVP_Shell/User }
>> Conflicts start where information lacks.
>> http://basconotw.mvps.org/
>>
>> Suggested posting do's/don'ts: http://www.dts-l.org/goodpost.htm
>> How to ask a question: http://support.microsoft.com/kb/555375
>
> The reason I was asking is two-fold : as I am using the HD for
> backups, it only needs to be connected to the power for about 1 hour a
> day while the backup runs. At the moment, the drive spins up whenever
> I go into Explorer, for example, and I have heard that spinning up and
> down can damage the disk. Also, because of the shortness of the USB
> lead, the drive has to stand close to the front of my CRT monitor. I
> know that these monitors have a magnetic field, so wondered if it
> could be a problem - although a device which sits on a desktop
> *should* have some sort of shielding, I would have thought (?)
>
> Thanks for the replies
> Kate
>
Hard drives are resistant to erasure by adjacent magnetic fields. If
there was going to be an issue, it would be if the switching noises
from the flyback of the CRT, got coupled into the controller board
on the hard drive. (I had a TV set years ago, that if you waved a
fluorescent tube near the side of the set, it would light up. That
would be an example. But at least some computer monitors are
shielded on several sides, making that less of an issue. My Sony
has a plastic outer shell, and metal boxes inside to hold stuff,
so that helps contain that kind of interference.
Otherwise, it is pretty hard to completely erase a drive with an
externally applied magnetic field. An article I was reading on
secure erasure of hard drives, claims that for the latest generation
of drives, they can no longer guarantee that commercial degaussers
are powerful enough to be certified to do the job. Sitting next
to your CRT, the field is not quite as powerful.
Hard drive storage is non-volatile, so the drive does not need to be
powered to retain its contents. If you use the "Safely Remove" icon
for example, that flushes the cache and prepares the system for
proper removal. Then you can unplug it, and put it away.
In terms of "start/stop" rating, hard drives now have a boiler plate
spec, that the drive is rated for 50,000 start/stop cycles. So if
the drive "wakes up" and spins up, and later spins down again, you
can do the arithmetic and figure out how many years it can sustain that
kind of usage.
HTH,
Paul
My thanks to