FLFI Stands for "File Level Fault Isolation" and is a volume group designation where files from a single directory will be saved entirely to one LUN in the volume group in a round robin fashion. So it spreads files on all the LUNs.
This is great for compressed video workflows or lower bandwidth video stream storage.
The term "fault isolation" derives from the opposite of "stripe" set. In a stripe set, if 1 LUN fails, all files in the stripe will be offline because files are striped across all LUNs of the stripe set. With FLFI, if one LUN fails, just the files that are stored on that LUN are offline - until the LUN is recovered.