I'm Home Sick Today

...so I have the time, and inclination, to stare dimly and uncomprehendingly at things for long periods of time. And eventually, I learn something.

See, I have a VM running Linux which handles the storage of Cloud Camera pictures. And once a day it generates the time-lapse movie of the day's pictures. And because I'm a sysadmin who believes if you don't measure it it didn't happen, I'm running software on that VM which records how busy the VM is and what it is doing.

Which led me to stare dimly at this graph for a while:

...which records the ethernet activity on the VM over the last day or so.

So what you need to know to make sense of this graph is that the camera is an IP camera, looking outside at the clouds going by, which FTP's an image every six or ten seconds (I can never remember which and can't be bothered to check right now) to the VM. This happens from around 5AM until around 9PM every day.

(The end result of which occasionally winds up here.)

But why is there more traffic in the early morning and the late afternoon? Look, it repeats every day:

And then it hit me: it is dark in the early morning and from late-afternoon on.

This IP camera has a night-vision mode which isn't entirely useless. It can see in the dark pretty well -- but the images it produces in the dark are bigger, because the noise in the CCD sensor can't be as efficiently compressed by the JPEG algorithm when the picture is predominantly dark.

And I'm rather pleased by that deduction.

Of course, I'm home sick, so my standards of "what is interesting" are probably somewhat looser than they usually are.