Hm. I suppose it's to late to talk to you about backups?
The disc sounds like it is constantly doing a quick spin all the time... as if a clock was ticking.
Sounds to me as a broken disk. When your data is really valuable, you should take the disk to a professional data recovering company, but that will cost you several hundreds of euros at least.
When you're not that desperate, take the disk out the NAS, put it in an USB enclosure, and connect it to a Linux PC. (Any PC booted from a Linux Live CD
or -usb stick will do).
Maybe you're lucky and is the problem in the Lacie's power supply. In that case you can read the disk without problems. When that doesn't work then *maybe* you can use ddrescue
to create a low-level copy to another disk. (You'll need an empty disk, which is at least as big as your NAS disk).