blog/data/2009-02-20-barcodes.txt

   1 Title: Using bar codes at a computing center
   2 Tags: english, nuug
   3 Date: 2009-02-20 08:50
   4
   5 <p>At work with the University of Oslo, we have several hundred computers
   6 in our computing center.  This give us a challenge in tracking the
   7 location and cabling of the computers, when they are added, moved and
   8 removed.  Some times the location register is not updated when a
   9 computer is inserted or moved and we then have to search the room for
  10 the "missing" computer.</p>
  11
  12 <p>In the last issue of Linux Journal, I came across a project
  13 <a href="http://www.libdmtx.org/">libdmtx</a> to write and read bar
  14 code blocks as defined in the
  15 <a href="http://en.wikipedia.org/wiki/Data_Matrix">The Data Matrix
  16 Standard</a>.  This is bar codes that can be read with a normal
  17 digital camera, for example that on a cell phone, and several such bar
  18 codes can be read by libdmtx from one picture.  The bar code standard
  19 allow up to 2 KiB to be written in the tag.  There is another project
  20 with <a href="http://www.terryburton.co.uk/barcodewriter/">a bar code
  21 writer written in postscript</a> capable of creating such bar codes,
  22 but this was the first time I found a tool to read these bar
  23 codes.</p>
  24
  25 <p>It occurred to me that this could be used to tag and track the
  26 machines in our computing center.  If both racks and computers are
  27 tagged this way, we can use a picture of the rack and all its
  28 computers to detect the rack location of any computer in that rack.
  29 If we do this regularly for the entire room, we will find all
  30 locations, and can detect movements and removals.</p>
  31
  32 <p>I decided to test if this would work in practice, and picked a
  33 random rack and tagged all the machines with their names.  Next, I
  34 took pictures with my digital camera, and gave the dmtxread program
  35 these JPEG pictures to see how many tags it could read.  This worked
  36 fairly well.  If the pictures was well focused and not taken from the
  37 side, all tags in the image could be read.  Because of limited space
  38 between the racks, I was unable to get a good picture of the entire
  39 rack, but could without problem read all tags from a picture covering
  40 about half the rack.  I had to limit the search time used by dmtxread
  41 to 60000 ms to make sure it terminated in a reasonable time frame.</p>
  42
  43 <p>My conclusion is that this could work, and we should probably look
  44 at adjusting our computer tagging procedures to use bar codes for
  45 easier automatic tracking of computers.</p>