USB HD problem

[Andrea Venturoli]

Hello.

On a server I manage, we use an external WD USB HD to make backups.
This has been working properly for two years.

Now it's getting hard to recognize the HD when it's plugged in: 
camcontrol will show the "pass" device, but no "da" comes up.

On the same box, another very similar HD still works fine.

So I tried this HD on several other machines and the conclusion is that 
on two Windows ones it always works, while on five FreeBSD I see very 
different results, ranging from always recognized to never recognized. 
On a couple of box it takes three or four tentatives before da0 comes up.

When the disk is not recognized (pass, but no da) I get:

> kernel: (probe0:umass-sim0:0:0:1): INQUIRY. CDB: 12 00 00 00 24 00 kernel: (probe0:umass-sim0:0:0:1): CAM status: CCB request completed with an error
> kernel: (probe0:umass-sim0:0:0:1): Retrying command
> kernel: (probe0:umass-sim0:0:0:1): INQUIRY. CDB: 12 00 00 00 24 00 kernel: (probe0:umass-sim0:0:0:1): CAM status: CCB request completed with an error
> kernel: (probe0:umass-sim0:0:0:1): Retrying command
> kernel: (probe0:umass-sim0:0:0:1): INQUIRY. CDB: 12 00 00 00 24 00 kernel: (probe0:umass-sim0:0:0:1): CAM status: CCB request completed with an error
> kernel: (probe0:umass-sim0:0:0:1): Retrying command
> kernel: (probe0:umass-sim0:0:0:1): INQUIRY. CDB: 12 00 00 00 24 00 kernel: (probe0:umass-sim0:0:0:1): CAM status: CCB request completed with an error
> kernel: (probe0:umass-sim0:0:0:1): Retrying command
> kernel: (da0:umass-sim0:0:0:0): got CAM status 0x44
> kernel: (da0:umass-sim0:0:0:0): fatal error, failed to attach to device
> kernel: g_access(918): provider da0 has error
> kernel: g_access(918): provider da0 has error
> kernel: (probe0:umass-sim0:0:0:1): INQUIRY. CDB: 12 00 00 00 24 00 kernel: (probe0:umass-sim0:0:0:1): CAM status: CCB request completed with an error
> kernel: (probe0:umass-sim0:0:0:1): Error 5, Retries exhausted 

I fail to understand the above codes.
Searching the web only yielded a result in German, but AFAICT it's a 
similiar problem, not the exact one I have.
Can someone shed some light on them?

Any other suggestion?

  bye & Thanks
	av.