[ioltas]

When it comes to backup, the time it takes for the backup to complete is not a property that matters the most in my opinion. The time it takes to restore the backup matters, and being sure that the backup is able to restore and is not corrupted matters even more.

[tomatocracy]

A backup which takes so long that the user aborts it before it completes (say if it's from a laptop to an external USB drive and user wants to take the laptop out with them) IS a problem though.