Using your iPod as a storage drive
If you use your iPod as a disk with a Windows PC, keep in mind that the FAT32 file system can only accommodate files that are smaller than 4 gigabytes. No matter how much free space there is on your iPod, you can't copy files that are larger than that.
While that note is for '
iPod' it probably applies to '
iPhone' as well.
Meaning, I don't expect iPhone to use NFTS or ext* formats.
With an iPod, you have the option to Format to NTFS;
Which does not make sense with iPhone -- it would no longer be a phone I guess.
Now, if you were to partition the iPhone space in some way to 'carve' out a new NTFS, ext2/3/4 partition on it, that might let you write larger files -- of course, you'd need to carve out more that your target files size in the first place.
Finally, if you just want to carry your large file on the iPhone (not play it there),
you could split the file into smaller chunks (GNOME split is one example, there are many tools for this).