Hugo Kornelis (3/29/2010)
As far as I know, it stops as soon as it reaches the end of the log file. That means that, in theory, you could envisage a scenario where the log file grows faster than the backup can read it, and the backup won't terminate. Though I am pretty sure that in practice, you'll never be able to make that happen.
That is not possible, no. The backup operation only requires log records up to the point that the backup data read completes.
See Understanding SQL Server Backups by Paul Randal for a neat diagram to explain that statement visually.
Paul White
SQLPerformance.com
SQLkiwi blog
@SQL_Kiwi