Petter Reinholdtsen

Using bar codes at a computing center
20th February 2009

At work with the University of Oslo, we have several hundred computers in our computing center. This give us a challenge in tracking the location and cabling of the computers, when they are added, moved and removed. Some times the location register is not updated when a computer is inserted or moved and we then have to search the room for the "missing" computer.

In the last issue of Linux Journal, I came across a project libdmtx to write and read bar code blocks as defined in the The Data Matrix Standard. This is bar codes that can be read with a normal digital camera, for example that on a cell phone, and several such bar codes can be read by libdmtx from one picture. The bar code standard allow up to 2 KiB to be written in the tag. There is another project with a bar code writer written in postscript capable of creating such bar codes, but this was the first time I found a tool to read these bar codes.

It occurred to me that this could be used to tag and track the machines in our computing center. If both racks and computers are tagged this way, we can use a picture of the rack and all its computers to detect the rack location of any computer in that rack. If we do this regularly for the entire room, we will find all locations, and can detect movements and removals.

I decided to test if this would work in practice, and picked a random rack and tagged all the machines with their names. Next, I took pictures with my digital camera, and gave the dmtxread program these JPEG pictures to see how many tags it could read. This worked fairly well. If the pictures was well focused and not taken from the side, all tags in the image could be read. Because of limited space between the racks, I was unable to get a good picture of the entire rack, but could without problem read all tags from a picture covering about half the rack. I had to limit the search time used by dmtxread to 60000 ms to make sure it terminated in a reasonable time frame.

My conclusion is that this could work, and we should probably look at adjusting our computer tagging procedures to use bar codes for easier automatic tracking of computers.

Tags: english, nuug.

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