It will even warn you if you haven’t connected to the drive for ten days or so. If it regains connection Time Machine will generally start copying files immedia

It will even warn you if you haven’t connected to the drive for ten days or so. If it regains connection Time Machine will generally start copying files immediately (and quietly). I’m not aware of situations where you would have to micromanage Time Machine. One bad thing about keeping your Time Machine drive disconnected for long is that Time Machine will eventually lose the thread. FSEvents logs every change to the filesystem and tells Time Machine which folders have changed. Consequently Time Machine ordinarily doesn’t have to search the whole disk for changes, it knows at all times what has changed and what to backup. Logging can, however, fail from time to time, the longer the backup drive has been disconnected, the likelier that becomes. Time Machine then has to search the whole disk for changes which is time consuming and resource intensive. Connecting to the Time Machine drive only infrequently is not a nice experience, the hourly backups are usually no big deal. Here is a great writeup about FSEvents and Time Machine on Ars Technica (part of John Siracusa’s epic OS X Leopard review): http://arstechnica.com/apple/reviews/2007/10/mac-os-x-10-5.ars/14 http://arstechnica.com/apple/reviews/2007/10/mac-os-x-10-5.a...; http://arstechnica.com/apple/reviews/2007/10/mac-os-x-10-5.ars/7 http://arstechnica.com/apple/reviews/2007/10/mac-os-x-10-5.a...