I/O bound, what is it, and what can be done about it?

Treah Blade treah.blade at gmail.com
Tue Sep 13 17:29:44 PDT 2011

On Sun, 11 Sep 2011 17:51:49 -0700
Nathan Coulson <conathan at gmail.com> wrote:

> Something I have been thinking about,  My computer can be near
> unusable if I am doing too much I/O tasks at once (let's say writing
> 0's to one drive, while running a backup on another [using two hard
> drives]).  Programs that do not use hard drives at all are almost
> unusable.
> [and if you are curious why I was doing that,  Was recovering data
> from a dying harddrive for a friend, and wanted to ensure the "new"
> ancient harddrive (40GB) I salvaged was stable].
> Compared to earlier systems,  my machine feels like a powerhouse (AMD
> 890GX w/ Integrated Graphics, Phenom ][ 945 processor [X4, 3GHz], 4GB
> 1333mhz Ram, 60GB OCZ Vertex 2 SSD).  Was surprised when I realized I
> can slow it down without even using the processor.
> although, i recall my AMD Duron 800Mhz system felt like a powerhouse
> as well...  but mycommon  workload seems to consist of openbox,
> firefox, urxvt, vim, and compiling software packages.
> What am I seeing?  What defines the limit of I/O Traffic on a system?
> -- 
> Nathan Coulson (conathan)
> ------
> Location: British Columbia, Canada
> Timezone: PST (-8)
> Webpage: http://www.nathancoulson.com
> -- 
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Ahhh yes but your processer is being used when you are transfering files around, because all disk IO calls have to be routed by the Operating System in a protectecd mode OS ( like linux ). Also any new programs that you are running may need to access the drive and thus will be slow as well. Another consideration are the system buses on the board that may be in use (albit not by the CPU) but by other hardware and thus the CPU has to wait to use the bus. The question as to why your system starts to become sluggish is complicated and simple at the same time. 

Treah Blade <treah.blade at gmail.com>

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