Backing Up User Data when data is not in use. Should I be concerned?

Question

This may be a dumb question. I would like to use duplicity to make backups to Amazon S3 of directories, each of which contains a different user's data. Each directory could be written to at any time. So I have two questions:

Should I be concerned that a scheduled backup of a directory might occur in the middle of data being written to files in the directory, resulting in a corrupted backup?

And if that is a valid concern, how would I go about temporarily delaying an operation while IO was happening, to try to minimize that effect.

Thanks for the advice

Answer 1

To provide part of the answer to my question, it looks like I can use lsof +D /directory/tree to see whether any processes have any files in a directory open.