Modern hard disks generate substantially more heat than they did in the past. Larger capacity drives do more work behind-the-scenes than smaller units, and the mechanism spins faster than ever before.
All these factors combined create very hot drives.
LaCie drives use two technologies to keep cool.
The case design is usually the reason the drive feels warm. Heat from the drive is moved to the outside of the enclosure, where it is carried off by air movement. This translates to a very warm external enclosure. This is normal.