Ever since they hit the mainstream consumer market in the late 2000s, SSDs have proven to be one of the most popular upgrades and add-on options for new systems. If you’ve used one, it’s easy to see why. The gap between the speed of the CPU and the speed of traditional spinning media is so huge, systems that are far too old for gaming or high-end business tasks still benefit from faster storage. SSDs have advanced at a fairly rapid clip over the last six years, including the recent debut of 3D NAND, which promises to significantly improve SSD density over the next 5-7 years. Unfortunately, these improvements have also hatched a cottage industry of rather radical claims regarding what’s possible in the longer term.

The latest report from Jim O’Reilly posits that 3D NAND is a fundamental game-changer for SSD capacities, with SSDs “nearly catching” hard drives in total capacity this year, surpassing them in 2016, closing to price parity on 2016, blowing past HDDs on every metric (including reliability and data retention), and taking over the storage market entirely by 2016, 2017 tops.

It’s true there are some potent trends driving SSD adoption and we expect to see more systems shipping SSDs as opposed to hard drives in the long-term, but the sweep that O’Reilly posits will occur in short order simply isn’t going to happen — at least, not as quickly as he predicts.

Hard drives vs. SSDs: The long-term view

First, while it’s true that SSD capacities should jump from the advent of 3D NAND stacking, hard drive capacities aren’t standing still. 20TB drives are expected by 2020, possibly assisted by HAMR (heat-assisted magnetic recording). Helium drives, pioneered by HGST, also have the ability to allow for further drive stacking, increasing capacities without a corresponding increase in areal density. A 1TB SSD today can be had for as little as $349, but a 1TB HDD from NewEgg is $48 for a laptop drive — which means you can bet Dell, Lenovo, and HP don’t pay anything like that much for the same capacity.

The cost difference between SSDs and HDDs has fallen dramatically in recent years, but it’s not expected to keep falling at the same rate. For argument’s sake, however, let’s assume that by 2017 the price of an SSD has fallen to 15 cents per GB — less than half the current price tag, while HDD prices have declined to about 2.5 cents per GB. A 4TB HDD, at these prices, would cost ~$100 — while a 4TB SSD would be around $600.

A look at today’s market is also useful. If SSDs were likely to make such a powerful play for ascendancy in the near future, you’d already expect to see them dominating laptops in the sub-$1000 price bracket. In reality, most $600 – $800 systems — systems that could absolutely “afford” an SSD — still rely on conventional spinning disks. Only above the $1000 point do you see SSDs making much appearance (and Gartner backs this up, noting that just 15% of laptops use SSDs today). Manufacturers, having primed buyers to look for storage capacity as a meaningful differentiation point, have been slow to switch and emphasize storage performance over capacity. That’s not going to magically change in the next 12-18 months.

As SSDs get cheaper, we will see higher capacity drives and better market adoption, but the one thing hard drives are really, really good at is storing tons and tons of data. The more data you need to store, the better hard drives are going to continue to look. Data centers, personal media centers, and storage racks are going to be some of the last places to convert to an all-solid state configuration, particularly when they can realize the benefits of SSD performance with intelligent caching systems that store “hot” data on SSDs and keep cooler data on slower, high-capacity drives.

As for the idea that SSDs will kill tape drives, it’s a laughable argument. Each type of storage in the market fulfills a clear, defined niche. Hard drives aren’t fast, but they have superior reliability (in some areas), preserve data when unplugged indefinitely, and are vastly cheaper than solid state storage. Sony and IBM have demonstrated tape with capacities of up to 185TB — if the advent of hard drives didn’t kill tape, thanks to its unique characteristics, the advent of SSDs isn’t going to, either.