I use a WD 2TB NTFS with .iso in PS3ISO folder, in my PS3 Slim Rebug 4.82.1.
I have it in a Salcar Usb 3.0 Enclosure. Not needed 3.0 but i use it also for pc, and anyway this box, works fine, another box from china, doesn't works very well, too slow with ps3 but also with pc. (so the box is important for the speed, sometimes about recognition.)
I hope this help.
I didn't like iso split because didn't know if online can be more risk than .iso in a single file.