The Dropbox API allows files up to 150Mb to be transferred, but that's not the only restriction. The other restriction is the PHP timeout. It's usually set at 30 seconds. With a typical upload speed from your server to Dropbox at 1Mb/s, a part size over 25-30 Mb is bound to cause a timeout error. The only way to transfer a single, big file is to not be bound by PHP's timeout, i.e. using the command-line backup.php script.
Nicholas K. Dionysopoulos
Lead Developer and Director
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