I/O performance for Flatbed Scanner

["Rich Braun" <user=44@nabble.blu.org>]

 Laura Conrad <[hidden email]> wrote: 
> So back to my other question, would doubling the memory from 1G to 2G 
> help? 

Three suggestions... 

(1) Using the program 'top', look at a parameter called '%wa' before and 
during  your scanning.  (If you have a a multiple-cpu system, press the '1' 
key to break down the display by processing core; 'top' reports misleading 
results on multiple CPUs, specifically it will show 25%wa on a maxed-out 
quad-CPU system.)  Also look at the 'used' parameter for Swap, and the 
VIRT/RES columns for the scanning program.  From this information you'll be 
able to tell if you've run out of system memory.  In particular, you should 
not be using much if any swap, and the VIRT size of the scanning process 
shouldn't be hugely greater than physical RAM.  Note that if it's sufficiently 
huge, even doubling physical memory won't help enough. 

(2) In your package-manager utility, install a package called 'sysstat'.  That 
will give you a utility called iostat.  I like to run the command 'iostat -k 
-d 5' while running a particular program to see how much disk activity it's 
generating across each drive. 

(3) If you have doubts about drive performance, or if you want to compare two 
dissimilar drives or RAID subsystems, download a simple-to-install utility 
called 'sysbench'--compile and run it on your system. 

-rich 


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