Every modern operating system has inotify-like capabilities. Mac OS has an integrated desktop search since 2005, which wouldn't be feasible without filesystem events.
Dropbox has its own process though, doesn't it? dbfseventsd.
sudo fs_usage -w
I've been watching it recently and it seems to touch files that it shouldn't need to. I need to do more investigation. I uninstalled backblaze recently because I discovered that it manually scans the whole filesystem _all the time_.
Thanks for the Backblaze info! That's really good to know. Do you know if CrashPlan is any saner? Resource usage was a big factor when deciding between the two, and I want to know if I've made the right choice :)
Interesting question - I hadn't gotten around to checking the numbers yet myself. So,
Indexes are stored in S3, data is on Glacier
~450GB of data stored
316,189 Requests to upload it all (main cost)
$17.39 to upload it all
$5.09 to store it last month (but upload was incomplete)
Expect closer to $6-$7 to store it this month
~$120 to restore it all (that was a back of the napkin figure before I started)
Arq has a number of good things to recommend it. The creator lurks around here, which is always nice to know. The design is very sensible - it's basically a git index on S3 with the data blobs in Glacier. The storage format is open and documented. All the data is encrypted using your own key locally and then pushed to your own AWS account. It works out really cheap if you use Glacier (only planning on restoring in catastrophic circumstances).
It all just works. The interface is easy and intuitive. I pushed my data to the EU region since it's closer. The more I think about it the happier I am with my choice at the moment. Even if I changed my mind and stopped using it - it's nice knowing that for a few dollars a month I have a huge snapshot of my data in a reasonable format in my AWS account.