few things to consider...
RAID1, or mirrored RAID, is when reliability is more important than performance.
you get all your data copied across all drives in the array so effectively, in a 2 drive array, all I/O gets doubled.
that would be one reason behind your 9hour process.
another would be the connection method.
be it USB2, USB3 or ethernet, all are huge I/O bottlenecks compared to internal 6GB SATA3 connections.
if you are using ethernet, make sure the LaCie and your PC have gigabit ports.
was there a reason you defragged a drive that had 0% fragmentation?
obviously, there is no benefit in doing so, so really all you are doing is giving your drives 9 hours of unnecessary activity.
I defrag my HDD maybe once every 6months. I tend to use the percentage of fragmented files as a guide and if it's more than 20%, it's time for some housekeeping.
and even then, I just select the worst offenders and tell DF to only defrag those.
otherwise, you are not only getting your defrag software to rearrange the fragments, your are relying on it's internal calculations to re-arrange all your files based on some 'best fit' algorithm.
also consider what the LaCie is used for and whether is needs any defragging at all.
for example, if it's used for backups, or media streaming, or some other sort of 'data dump' repository, defragging becomes almost unnecessary.