With a distributed storage system you should be able to read said terabyte file using far more disk heads. It would also be easier to engineer it so the teraby

With a distributed storage system you should be able to read said terabyte file using far more disk heads. It would also be easier to engineer it so the terabyte file was entirely in RAM by distributing it across multiple machines (although single machines with TB ram capacity are no doubt continuing to become more common) Sure, store it on a single tape or disk and distributing the computation won't help. You need distributed storage to properly leverage distributed computation for otherwise I/O bound processes.