USB device activity when not mounted

Gary Aitken freebsd at
Sat Jun 16 05:38:37 UTC 2012

On 06/15/12 03:23, Thomas Mueller wrote:
>> I can understand why I would see activity on a USB device when it's first plugged in.  But why do I see continued activity (i.e. the light blinks on a usb disk or memory stick)?  When I umount one of these, they keep being beat up on and it makes me nervous...  At what point is it sync'd and safe to unplug?  I assume when the umount returns, but what's going on after that?
> I had that problem/quirk with a SanDisk Cruzer 8 GB USB stick.

Heh.  My 4 gig one does it too.  However, so does my seagate usb hard drive, so it's not specific to one mfg.

On 06/14/12 07:49, Daniel Feenberg wrote:

> Is it possible that there is volitile memory buffering in the stick that may not have been written to flash when umount thinks it is complete, and the flashing light is an indication that power is still required to complete the write to non-volitile memory?

I'm pretty sure that's not it.  My devices (memstick and usb disk) will blink happily for hours.  Well, minutes, anyway.  I haven't got the patience to wait it out beyond that...

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