Solid state drives appear perfectly positioned to take over the storage market from physical hard disks as technology advances. There will long be a place for the mass storage provided by spinning disks, but as SSD prices drop and storage values increase, they'll transition from luxury to mainstream. At least, that's the expectation.

A research project from the University of California, San Diego paints a different picture: as SSD storage densities increase, read speeds and reliability will decrease. The study author claims that by 2024, when NAND flash is expected to operate on a 6.5nm transistor process, solid state storage will hit a wall--increasing capacity after that point will unacceptably damage performance.

NAND flash storage reliability, speed and volume are all interconnected issues. Currently solid state storage operates on 25 nanometer transistors. As transistors shrink, more of them can be fit onto a chip. Storage volume goes up. But the smaller the circuitry, the smaller the walls between electrons that form bits of data. When those get too small, data leakage can occur, decreasing reliability.

The study concludes that SSDs will grow to support more storage and cost less per bit, but that their actual performance will degrade as those factors are improved.

To make things more complicated, SSDs are made from single-level cells, which hold one bit of data per cell, multi-level cells, which hold two bits, and triple-level cells, which hold three. TLC NAND storage obviously offers the most storage in the smallest size, but is more prone to error.

Based on their study of 45 current flash chips, the researchers extrapolated that latency in the TLC chips of 2024 manufactured at 6.5nm would increase by 2.5 times. MLC latency would double, and bit errors would more than triple. The projection called for TLC solid state drives to store up to 16TB of data.

SSDs can only perform so many program-erase cycles before dying out. The researchers predict those lifetimes--currently measured in thousands or tens of thousands of cycles--will lower as densities increase.

The study concludes that SSDs will grow to support more storage and cost less per bit, but that their actual performance will degrade as those factors are improved. All of these projections are based on current solid state technology, though--that gives the tech industry 12 years to come up with groundbreaking advancements before running into the predicted performance wall in 2024. That's plenty of time to design more effective and speed-efficient storage systems, right?