Most 2.5 external drives these days are USB3.0 with higher power supply requirement, and I also encountered read error even with Y cable. Go for 3.5 external ones with its own power supply if you face the same issue after using the Y cable.
@SylverReZ, @BigOnYa ok i read that the super slim model (the one i have) isnt compatible with cfw and that "HEN is the next best thing, it is a semi jailbreak applied on top of the OFW system software, it is geared towards console models that aren't CFW compatible, you can run homebrew, play backups but you cannot use customised system files & must reapply your customisations & HEN after every boot."