I have a Mac mini that I keep an external hard drive attached to. Recently I installed some online backup software that continuously uploads your changed files (including external drives). Around this time I noticed that the hard drive was spinning up and accessing data frequently. Usually just for a second or two at a time, roughly 1-2 minutes apart. I assumed the backup software was looking for changes. I contacted their support, but they told me their software doesn't work that way. That it would spin up the hard drive for indexing about once an hour. Skeptical, I uninstalled the software (using their uninstaller) to see if the problem continue. And it did. So perhaps the software isn't to blame. I tried disabling "Power Nap", but the hard drive still would spin up. Next I disabled "wake for network access", and this fixed the problem. But why? I would have thought that the backup software was waking the computer to upload files, but that software isn't even on my computer anymore. What else would be causing the computer to wake up that often, and spin up the hard drive with it?