Last time i used EXT3 for an 2TB volume, everythings fine but i need to disable the filesystem checks with tune2fs, because it needs too much time for an check :-). I´m not felling really good about that, is there a better solution?
Keep in mind if you go with XFS, you're going to need 10-15 gig of memory or swap space to fsck 6tb.. it needs about 9 gig to xfs_check, and 3 gig to xfs_repair a 4tb array on one of my systems.. oh, and a couple days to do either. :)
Mike