Windows: "Fast allocate" didn't seem to work for me too, I switched to "Full prewrite" since. The name fast allocate suggests the usage of
that's a unix tool, I don't know whether it's actually working at all on Windows as it is now.
There's certainly a need for Windows-custom code to make it work, not sure it's actually what Tixati is doing:
I recently moved all files from one drive to another using Tixati (worked like a charm actually! much better than uTorrent did at only fraction of files/size) and this topic made me check fragmentation. I expected all moved files to NOT be fragmented at all, but some of them are. Mostly multi-file torrents were copied in a fragmented state, single-file torrents appear to be alright. This here could be an OS problem (Windows), not Tixati.