Last week, on more than one ocasion, I could feel my laptop getting really hot for no apparent reason which pointed me to take a closer look at what’s using up my resources. Indeed CPU & memory were being intensely taken over by mds and md-worker (mkay, they weren’t really “taken over”, more like one core was and half a gig of RAM, but still quite significant). What are those, you ask? Well, they are processes related to Spotlight, that wonderful little tool on the Mac OS that just seems to know where everything is on your system. In order to do that though, it has to spend some time going through your new files so that it can find them quickly when you’re looking for them.

I was on the right track, but I couldn’t really picture any reason why Spotlight would be working out so intensely all of a sudden, as I hadn’t copied any large amounts of files or anything of the sort in the previous days. Even if I had, why would it take so long to index them (it was pretty quick with everything in the very beginning). It took a bit of searching around, but I eventually tracked down a bug that makes Backblaze (a cloud backup service) and Spotlight not play well together.

Here’s a description of the problem and very easy fix (on the Backblaze website! How cool is that? Good job tech team!); it boils down to Backblaze playing with a (large) log file very often which apparently makes Spotlight want to reindex it and results in a continuous load on that process. All you have to do is tell Spotlight to ignore that log file. Done, everything is back to normal.

(Note: It seems that Backblaze does try to tell Spotlight to ignore that folder when it installs, but sometimes it doesn’t work right. Maybe it’s a Lion-related bug? I don’t really know, but nonetheless, it’s good that they actually put up a description of the problem and fix on their website, I really liked that).