A better hard disk

Speaking of new ideas - here's one for external hard disks.

We have the regular hard disks at about $100 for 250GB, and the super expensive SSD disks.

The ones I like most - like the Western Digital Passport series - come as a nice small package and derive power from the USB cable, no external adapters required.

But these are slow.

Is it possible we can do the following:

- a RAM slot that the user can fill in - say, I put in a 2GB DDR2 piece in there, like my netbook

- a small battery - the iPod runs for hours and hours, surely a battery charged from the USB cable can store enough to run the HDD for some time

- some system software

Now, when I write to the disk, it will fill in the RAM first - just like a memory cache. This should be blazing fast. Then, at a slower pace, it will copy over the data to disk.

Because I have the battery backup, I am free to disconnect as soon as I've transferred data to the RAM, and the disk setup will take care of running on its own - disconnected - to transfer data to the HDD

Is that possible, or just an useless thought? By leaving the memory slot user-filled, costs should not increase much from the basic HDD - but perceived throughput certainly will.