Thanks for the suggestion @conrad
Do you happen to happen to know if both the database and Temp folder were on an SSD?
By default for a Duplicati non-service install, both of them are in user profile local AppData
tempdir shows how to move Temp. I don’t know if Recreate uses that temporarily or goes
directly to usual DB location at Database screen Local database path while recreating.
If it does go directly to usual path, the usual path can be moved to some faster location…
Theoretically a RAM disk might be even faster, but may be too small and is kind of volatile.
Measuring can find the bottleneck, e.g. Task Manager can watch how busy the drives are.
CPU is best looked at per-logical-processor (right-click graph). SQLite is single-threaded.
Backups suddenly taking much longer to complete got quite deep into system monitoring.
Above is simply looking at performance (which matters), and not so much on why it stops,
however if somehow a file download hung, pre-downloading files might avoid that problem.
Logs and error messages would of course also be helpful in figuring out where it fell apart.