Sorry if this has been posted before, I'd have searched about but couldn't find any good advice I noticed today that Time Machine was switched of a few months ago, either by accident or bug, so I switched it back on and started a manual backup. After about an hour of 'preparing' it said the backup was too large for the backup disk... 'requires 418.3 GB but only 212.3 GB are available.' Thing is, the entire content of the drive I'm trying to backup up is only 414.29 GB, according to Time Machine preferences the actually data size of included files to be backed up (I've excluded a few folders) is only 356.5 GB. Ok, 356.5 GB is too big for the 212.3 GB available, but why does it say 418.3 GB are required? And at least 100 - 200 GB of content (my iTunes folder and apps for example) shouldn't have changed much since the last backup, even if it was a few months ago, so shouldn't need backed-up again? Should it?!