[jrockway]

A drive these days is a CPU, memory, and some flash chips. If the CPU and memory are swappable (isn't in consumer SSDs, no idea about enterprise), then one drive today is really many independent pieces of storage media. Thus, you'd imagine the failure case to be more like the failure case for one entire storage server (pipe drips on it, tornado sucks it up) rather than worrying about the failure case for mechanically-linked hermetically-sealed platters spinning at high speed.

There is always the chance that all the flash chips fail at the same time because of a manufacturing defect. That has always been the gamble over multiple drives as well; many documented cases of all the drives in a RAID array failing at the same time. (This happened to me once! Terrible shipping from NewEgg damaged all 3 drives in my 3x RAID-1 array. I manually repaired them by RMA-ing the disks one at a time; fortunately different blocks failed on different drives and with 3 drives you could do a "best of 2".)

No matter how many independent drives you have, you will always need your data stored in multiple data centers to survive natural disasters. So I don't see 256TB in one device any differently than putting 32 8TB SSDs in one server. If you need that much storage, you spend less of your day plugging it into your computer. Savings!