Arno Lehmann wrote:
Hello,
On 06.10.2005 09:30, Sebastian Stark wrote:
On Thursday 06 October 2005 00:11, Arno Lehmann wrote:
(If you really want to use
external disks, use 2.5" drives for notebooks, and operate them with a
proper power supply.)
Why? Are 2.5" drives more shock-proof?
In general, they are.
Non-operating shock and vibration ratings for:
Hitachi TravelStar 5K80 2.5 5400 RPM 80GB
Shock (half sine wave, 1 ms): 800 G
Vibration (sine wave): 5.0G (22-500Hz)
Hitachi DeskStar 7K250 3.5 7200 RPM 250GB
Shock (half sine wave, 2ms): 350 G
Vibration (random (RMS): 1.04 G rms (XYZ)
It appears the 2.5 mobile drives are designed to withstand greater shock
and vibration than desktop drives, although Hitachi's numbers may be
misleading. Notice they gave a 2 ms shock rating for the DeskStar and
only a 1 ms rating for the TravelStar, a 3 dimensional random vibration
rating for the DeskStar and a sine wave (2 dimensional?) rating for the
TravelStar. Interesting. Marketing reasons, perhaps? Anyway, it would
seem the mobile drives are more shock resistant than the desktop drives,
but maybe the difference isn't as drastic as at first appears.
I'm asking because I sometimes exchange big datasets with people by
sending standard 3.5" drives, e. g. from Germany to Australia and
back and had no problems so far. Luck?
That depends on the packaging. I've seen 3.5" disks damaged after
sending them by mail when not properly protected, and - more important
in case of the backup scenario - the disks are damaged easily by
dropping them. A few cm can be enough. One of the reasons why I prefer
tapes. (Although SLR/MLR/QIC cartridges don't like being dropped or
shaken, too, but that can be fixed by retensioning them.)
Especially when handling disks without protective packaking you should
be careful when putting them on a shelf, even.
(From my days as a salesperson: We made the experience that disks that
were delivered in the original box and stored and handled in their
manufacturers plastic cases had much less warranty cases than the ones
that came packed in antistatic bags only. A good reseller will only
transport disks in the manufacturers special packaging, like SeaShell
from Seagate for example.)
Back to backup use: If you need 3.5" disks (for example because of the
available capacity) you should use the ones sold by the manufacturer
as external drives, and not sinply put a disk into a cheap case. And
make sure the storage where you keep hem has a soft ground.
Arno
-Sebastian
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