On Mon, 21 Jan 2008, Guennadi Liakhovetski wrote:

> Hi
> 
> My external USB disk has never been 100% reliable, but since recently it 
> seems to be causing USB resets more often than before. Therefore a couple 
> questions:
> 
> 1. Is it dying? should I look for a replacement?

Maybe.  It depends on what is causing the resets.

> 2. Before, if such a reset happened when the disk was mounted it 
> definitely meant SCSI errors, most probably, a disconnect. Now (2.6.22 
> Debian kernel) these resets seem to be handled transparently - no SCSI or 
> fs errors, just a delay in data transfer and then it just continues. Is it 
> indeed a (relatively) new feature?

New since about 2.6.10.  :-)

> How normal is it?

On a well-working system it isn't normal at all.  Resets like that are
a sign of something wrong.  It could be at the electrical level (cable
connections or power levels), firmware level, media level (read/write
errors), or possibly elsewhere.

> And how reliable is 
> the recovery? Well, I presume it should be reliable since there are no 
> SCSI / fs errors, but...

For certain classes of errors it is quite reliable.  For others it 
doesn't help at all.  For example, if the drive's firmware has crashed 
then a reset isn't likely to help.

> In short - shall I worry or shall I not?:-)

Since the errors have been increasing in frequency, you probably should 
worry.

Alan Stern

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