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gbtestdisk

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Introduction

An important aspect of computer performance is the spead with which data are written to and read from the hard drive. To test hard drive speed I put together a little shell script, gbtestdisk. It measures the speed for synchronous writing and reading using the 'dd' command. Notice that this is an high level measure, that is it also takes into consideration the file system, the system buses and all other possible bottlenecks. For this reason, rates reported by this script are in general lower than the ones directly reported by dd. Indeed the rate reported by dd represents the rate without any lag or synch time. Time estimations by this script are a better approximation of the time effectively used by a program to open a file, write or read the content and close it. In this respect its measure should be a good approximation of the actual performances observed by the user.

Installation and use

To use it, simply download the file, move it in a directory with write permission and run the script to test the speed of the partition this directory belongs to. Depending on the directory where you place it, the script might require root permission, so be prepared to insert the appropriate password. The script accepts the following options

-h print this help
-c number of MB of the file size
-r number of executions of the write/read cycle
-v verbose output: print information about the performed tests

For instance to check the write, read and cache read for a file of 64 MByte use

gbtestdisk -c 64 -v

The output should be something like (this is the result on my laptop)

#       write MB/s      read MB/s       cache MB/s
max     170.212000      180.790000      2782.608000
min     33.437000       175.824000      2285.714000
avg     106.007400      179.391200      2570.997600

Typically the time necessary to write a file to the disk or to read it depends on its size. The two pictures below show how the writing/readings speed change with file size.

gbtestdisk_laptop.png

gbtestdisk_desktop.png

The plots above have been obtained with

for size in 16 32 64 128 256; do 
  echo -n "$size " ;
  ./gbtestdisk -c $size | grep 'avg' | gawk '{print $2,$3,$4}';
done | gbplot -T png -o "laptop.png" -v -l xy \
-C 'set key below; set xrange [15:300]; set xtics (16,32,64,128,256); set grid;\
set title "ThinkPad X201s"; set xlabel "MB"; set ylabel "MB/s"'\
plot 'u 1:2 title "write" w lp pt 5, "" u 1:3 title "read" w lp pt 5, "" u 1:4 title "cache" w lp pt 5'

Author: Giulio Bottazzi

Created: 2016-06-04 Sat 19:19

Emacs 24.3.1 (Org mode 8.2.4)

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