As much as I like LaCie, and have been a continual customer, I am not sure how their drives perform in RAID-1 operation, as I don;t know what kind of controller their newer drives use. I have several of their older RAID-0 drives, and I always feared the worst out of any RAID-0 used for data that is in any way important.
Please do report how the drives perform in RAID-1, and what you need to do in order to switch it over. I thought that the controllers in their enclosures only supported RAID-0 (striping).
I own three of ther 1TB RAID-0 enclosures, plus a 2TB version, and a LightScribe. Most of these are FW 800, which is perfect for my use.
They do use strange PSU connectors, and their power supply transformers are notorious for short lifespans, but LaCie is usually good about replacing them. I would suggest ordering a backup PSU to keep on the shelf, in the event that the factory unit dies, so that you have a backup while you wait for an RMA.
You may also wish to read about various RAID configurations, for future reference. I generally use RAID 0+1 (or RAID-10), as it provides the best level of stability and data protection of the common RAID levels/ (RAID-15 is the best in this area, but few controllers support it.)