Any LaCie direct-attached hard disk that is formatted HFS+ (Mac OS Extended) is compatible with Time Machine. A hard disk must be HFS+ formatted in order to work with Time Machine. FAT32 formatted hard disks need to be reformatted to HFS+.
Time Machine will only allow configuration of a single destination drive. Time Machine might recognize a FAT32 hard disk and prompt to reformat it, but for best results, follow LaCie instructions rather than allowing Time Machine to reformat the hard disk automatically.
Certain LaCie network storage devices are compatible with Time Machine, however, not all. Please verify in your product manual if your network device is Time Machine compatible.
To determine if a LaCie hard disk is formatted HFS+ for use with Time Machine, simply select Applications, then Utilities, then Disk Utility. Click on the disk’s icon on the left side of the window. It will show an icon for the top level of the disk, as well as the name for each partition/volume on that disk drive. At the bottom of the window, the Format should say "Mac OS Extended" (or "Mac OS Extended (journaled)") Its Partition Scheme should say Apple Partition Map for PowerPC-based Macs, or GUID Partition Table for Intel-based Macs.