Every internal hard drive I have bought in the last 5 years has had a single platter with the highest density I could find. As well as (in theory) better reliablilty, a single platter drive should consume less power, produce less heat and possibly be slightly quieter than an equivilent with multiple platters.
[Off topic - Warning, long monologue!:o]
Here are two rules of computing which in my experience are just as true today as they were 17 years ago when I had a 65MB hard drive:
1) Data will always expand to fit the space available.
2) Backup storage capacity will always be insufficient for the quantity of data which needs to be backed up.
So a hard drive which is significantly larger than you need will just result in more data, much of which needs to be backed up. And the only affordable device that currently has enough capacity to backup a large hard drive is another hard drive. Extra hard drives are very useful for fast, frequent backups and imaging whole partitions, but I don't trust them as the only storage medium for anything important.
I think that a proper reliable backup system should meet the following basic criteria:
1) The read/write mechanism and storage medium should be separate.
2) It should be (virtually) impossible for a malfunctioning read/write mechanism to destroy data on the storage medium. And when the storage medium suffers partial failure or damage any intact data should be retrievable.
3) There should be a hardware write protect system, and/or the option of using write once storage as well as rewritable (to guard against human error).
4) The backup medium should be adequately protected from accidental and enviromental damage (when handled and stored with reasonable care).
Hard drives fail every requirement. When the read/write mechanism or controller fails there is little the user can do, and often the platters are damaged or the data corrupted. You can try freezing the drive, changing the controller board etc., but there is a high risk of losing everything beyond any hope of recovery. A professional data recovery service could remove the platters in a clean room and use a scanning magnetometer to read them, but the cost is prohibitive and they can't always recover what was corrupted or damaged when the drive failed. Any magnetic storage medium is likely to fail the second requirement; I have twice had Zip drives which suddenly decided to destroy the entire contents of every disc that was inserted. Solid state drives and USB memory sticks have an integrated controller, and I expect that any flash memory based storage would fail the second requirement.
Optical storage could meet every requirement, but for the mass market manufacturers insist on using bare discs which are too susceptible to accidental damage. A Plasmon UDO drive would meet all the stated requirements, but at Â£1800 per drive it is much too expensive.
Will there ever be an affordable backup system that meets these requirements? Probably not. Does the thought of having hundreds of gigabytes of data which hasn't been backed up or archived scare me? It certainly does.:sad: