[citation][nom]sliem[/nom]Cool, soon it'll be 5TB SSD.Why is it not already 5TB SSD?[/citation]
1) nand memory is expensive, especially in high density solutions. at $1/GB a 5TB drive would be $5000. But because super high density memory is even more expensive you would really be talking about $10,000+
2) Controllers do not currently do more than 1/2 TB. If you see a drive bigger than 512GB then they have 2 controllers inside doing some form of RAID to provide the space. Multiply that out to a 5TB drive and you have a very complicated mess with far too many failure points involved. Thankfully 1TB controllers are coming next year, which will open up the door for 1TB mainstream drives, and 2TB specialty drives, but my bet is that it will stay at those storage points a few years before we see 2TB controllers and 4TB drives. So anything larger than 4TB on a consumer SSD will not be seen for probably 5-7 years. However, there will always be things like the OCZ Revo drives which offer much more capacity (I think you can order a 16TB Revo4), but you pay through the nose for such storage capacity.
3) Form factor. Simply put, this device has 1 controller chip, and 4 memory modules, which means that each module is holding 128GB of memory. Considering most chips are 128Gb (bits, not Bytes), we are talking about an 8 fold increase in density over your average memory size. That is also why it costs over $1/GB when mainstream drives are getting closer to 50-75 cents per GB. If you put these chips in a normal sized SSD you would see a capacity of 2TB (16 chips at 128GB each) if someone made a controller that could handle that kind of space.