linux-kernel - Re: 32GB SSD on USB1.1 P3/700 == ___HELL__

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Date:	Fri, 09 Apr 2010 08:56:04 -0700 (PDT)
From:	Ben Gamari <bgamari.foss@...il.com>
To:	Andreas Mohr <andi@...as.de>, Bill Davidsen <davidsen@....com>
Cc:	Andreas Mohr <andi@...as.de>, Jens Axboe <axboe@...nel.dk>,
	Wu Fengguang <fengguang.wu@...el.com>,
	linux-kernel@...r.kernel.org
Subject: Re: 32GB SSD on USB1.1 P3/700 == ___HELL___ (2.6.34-rc3)

On Thu, 8 Apr 2010 22:35:26 +0200, Andreas Mohr <andi@...as.de> wrote:
> On Thu, Apr 08, 2010 at 04:12:41PM -0400, Bill Davidsen wrote:
> > Andreas Mohr wrote:
> >> Clearly there's a very, very important limiter somewhere in bio layer
> >> missing or broken, a 300M dd /dev/zero should never manage to put
> >> such an onerous penalty on a system, IMHO.
> >>
> > You are using a USB 1.1 connection, about the same speed as a floppy. If 
> 
> Ahahahaaa. A rather distant approximation given a speed of 20kB/s vs. 987kB/s ;)
> (but I get the point you're making here)
> 
> I'm not at all convinced that USB2.0 would fare any better here, though:
> after all we are buffering the file that is written to the device
> - after the fact!
> (plus there are many existing complaints of people that copying of large files
> manages to break entire machines, and I doubt many of those were using
> USB1.1)
> https://bugzilla.kernel.org/show_bug.cgi?id=13347
> https://bugzilla.kernel.org/show_bug.cgi?id=7372
> And many other reports.

Indeed. I have found this to be a persistent problem and I really wish there
were more interest in debugging this. I have tried bringing the community's
resources to bear on this issue several[1] times, and each time we fail to
get enough of the right eyes looking at it or developer interest simply vanishes.

I've started putting together a list[2] of pertinent threads/patches/bugs/data
in hopes that this will lower the energy barrier of getting up to speed on
this issue. Hopefully this will help.

Cheers,

- Ben


[1] https://bugzilla.kernel.org/show_bug.cgi?id=12309
[2] http://goldnerlab.physics.umass.edu/wiki/BenGamari/IoWaitLatency

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