Help troubleshooting...

Warner Losh imp at
Mon Oct 26 10:24:06 UTC 2009

But there was no indication the device went missing on the console.  
And it wasn't until I unplugged it that da0 detached. Usually in the  
past when it has started throwing errors the console was chatty about  


On Oct 26, 2009, at 2:59 AM, Hans Petter Selasky <hselasky at>  

> On Monday 26 October 2009 01:05:03 non at wrote:
>> M. Warner Losh wrote:
>>> I have a usb stick (8GB) on it.  This stick has about 5GB of junk on
>>> it at this point.
>>> I tried to do 'cat * > /dev/null' recently, to measure how fast it
>>> goes.  It got about 1GB into the drive and then I got device missing
>>> messages.
>>> So devfs thinks the device went missing:
>> Warner-san, maybe it is caused by the hardware problem on the USB  
>> flash
>> memory. Some chip on the memory might have too much heat when you  
>> access
>> the memory at fast rate. Then it stops working.
> What happens if you read from two USB disks at the same time?
> If the device went missing the USB HUB signalled that. This is maybe  
> an
> indication that the USB firmware on the device crashed. Maybe this  
> is due to
> heat, or unhandled race conditions when the load goes high.
> Try using "dd" and vary the block size from 512 to 65536 bytes. Does  
> it stop
> working with all block sizes over time?
> --HPS

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