USB hard drive not working

[Taras_96]

Hi everyone,

I have a laptop hard drive encased in a digimate II plus case, which
allows me to copy the contents of memory cards to the hard drive
without the help of a computer. However, windows seems very
temperamental in trying to recognise the drive. Last time I tried
using the hard drive, the two partitions were recognised and appeared
in my computer. Today the partitions are not appearing?! The
partitions were also mostly not recognised when I used the hard drive
on my travels (I assumed it had something to do with the WIndows
version being Chinese).

I'm using Windows XP home edition, service pack 2, fully updated. When
plugging in the hard drive, no bubbles appear in the system tray (eg:
'USB mass storage device found) but device manager shows, under
Universal Serial Bus controllers, 'USB Mass Storage Device' with a
yellow exclamation mark next to it.

Case in point: I just tried a different USB port, which wasn't
previously working, and now the hard drive partitions are recognised!!

Does anyone know what's happening, or how to diagnose what's
happening?

Thanks

Taras

 

[Taras_96]

Some more information:

I was browsing the contents when I got the following message popup in
the system tray:

"Windows was unable to save all the data for the file N:. The data has
been lost. This error may be caused by a failure of your computer
hardware or network connection. Please try to save this file
elsewhere"

I wasn't trying to write/copy/move any of the files on the hard drive.

Taras

 

[R. McCarty]

External drive enclosures usually employ a "Translator" chip that
provides a conversion from a Serial data stream to a traditional
PATA ( Assume your 2.5" drive is a Parallel ATA style ). XP
remembers each USB peripheral that is connected. If the device
is USB 2.0 then it doesn't matter which USB "Socket" the device
is plugged into. Internally the USB hardware detects the device
and routes it to a appropriate Controller/HUB. If however the
device is a USB-1(.1) then there are multiple Controller/Hubs to
provide the older USB 1(.1) capability. These are socket specific.
So if you plug it into socket #1 and move it to socket #4 XP will
re-enumerate (or detect it ) as a new instance of the device.

These external cases/enclosures vary wildly in how well they work.
It's not uncommon to experience issues like you describe.

 

[R. McCarty]

This usually means the device's Performance Policy has been changed
from "Quick Removal" to "Performance" - or had it's Write Cache
enabled. Write behind caching is susceptible to data loss and should
only be used when the PC/Device has some form of battery backup in
use. USB External drives can only achieve a sustained throughput of
around ~25 Megabytes-per-Second ( fairly slow ) so trying to use any
caching on them is not a good idea.

 

[RalfG]

If the drive is USB powered it's possible that a single port doesn't supply
enough power to run it properly. Sometimes an auxliary USB power-only cable
is provided with USB powered harddrives, to draw extra power from a second
USB port.

 

[Taras_96]

thankyou everyone for your replies

Going by RalfG's post, even though the hard drive is designed to be
fully portable (different to the 'portable' HDs you commonly get,
which are just a normal HD in a USB casing)) and thus power delivered
through a single USB port 'should' be sufficient, I tried plugging the
HD into the mains power. Sure enough, this seems to have fixed the
problem! Must be something weird going on with the power levels..

Taras