Re: umass intermittently "stalling" ... processes seemingly stuck in "wdrain" state

"Pascal Hofstee" wrote:
> I recently bought an USB Mass Storage unit (about 300GB) and a 4+1
> slot PCI USB2.0 card (since it's an old box that didn't have USB 2 on
> board yet), and i have noticed that intermittently the device "stalls"
> any operations that try to access it:
> 
> - copying data onto the disk
> - reading data from the disk
> - running an ls while inside a directory on the disk's mount point
> 
> Today while trying to scp a fairly large set of files from my office
> system to my umass disk at home i noticed the similar stalling
> behaviour and decided to check ps output on my home system. There i
> noticed that every single time to scp session would begin stalling
> (lasting up to about 30-40s per stall) ... the scp process on my
> home-system would have dropped into a wdrain state.
> 
> As soon as the scp process (after about 30 or more seconds) would
> finally get out of this wdrain state (usually into an sbwait state)
> the scp process on my work system would start picking up transfer
> speed again until the next slip into wdrain.
> 
> I haven't been able to test this on a non-CURRENT system yet so i am
> not sure wether or not this is a CURRENT only issue or a more generic
> problem, but if somebody could give some pointers on where to start
> looking on fixing this ... i am open for suggestions.

I've seen stalling on 1 of 2 x 6.1-RELEASE hosts.  I was given an
80 Gig external USB (Freecom) (disc reported to be unstable on XP,
but as I don't run XP ... :-). I ran disc for a long time OK via a
Zediworks USB2 powered hub, to a Belkin USB2 Cardbus on my laptop
with 6.1-RELEASE.

	No recent problems (OK, various USB2 devices on laptop used
	to cause crashes, (that didnt crash on the inbuilt USB-1),
	I assumed it was because Belkin overheating - card got too
	hot to touch in middle ! (My brother reckons his Belkin may
	have died in my laptop under FreeBSD, his identical laptop
	didnt kill his Belkin under XP - my guess was maybe FreeBSD
	wasn't switching Belkin card into idle state to keep it
	cool ? but that's another issue)).

Moved 80G drive to a direct connection on main 6.1-RELEASE tower.
Persistent hangs. umount -f would eventually work, then I did fsck
& mount, & repeated.  I didnt observe ps states. Moved disc back
to laptop, no hangs. I'd assumed hardware problem & thought next
to try moving hub too. Now I've read your post I'll look at PS
states too.

(My 80G drive is a 3.5" with own power supply, not a laptop drive
in external unpowered box needing more than the 0.5A delivered by
a USB connection.)

-- 
Julian Stacey.  BSD Unix C Net Consultancy, Munich/Muenchen  http://berklix.com
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