Hard-disk drive vendors point to the higher price of solid-state drives as a reason to keep on buying hard drives, but as Bob Dylan sang, "The Times They Are a -Changin'." The advent of 3D NAND has become a game-changer for the storage industry by increasing SSD capacity and dropping SSD prices.

By packing 32 or 64 times the capacity per die, 3D NAND will allow SSDs to increase capacity well beyond hard drive sizes. SanDisk, for example, plans 8 TB drives this year, and 16 TB drives in 2016. At the same time, vendors across the flash industry are able to back off two process node levels and obtain excellent die yields.

The result of the density increase is clear: This year, SSDs will nearly catch up to HDD in capacity. Meanwhile, hard drives appear to be stuck at 10 TB capacity, and the technology to move beyond that size is going to be expensive once it's perfected. HDD capacity curves already were flattening, and the next steps are likely to take some time.

This all means that SSDs will surpass HDDs in capacity in 2016. There’s even serious talk of 30 TB solid-state drives in 2018.

So what about SSD price points? In 2014, prices for high-end consumer SSDs dropped below enterprise-class HDD, and continued to drop in 2015. A terabyte SSD can be had for around $300. Moreover, this is before 3D NAND begins to further cut prices. By the end of 2016, it’s a safe bet that price parity will be close, if not already achieved, between consumer SSDs and the bulk SATA drives.

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This will put pressure on hard-disk drive makers to lower prices, but, frankly, they’ve used up most of the tricks to reduce cost and are already at single-digit margins for bulk SATA drives, so they don’t have much wriggle room.

With parity achieved in capacity and price, one has to ask whether HDDs will still be needed. SSDs are blindingly fast in comparison. Typically, large consumer SSDs are 5x the streaming performance and 5000x the random read/write rate. With low operating power and very low standby power, SSDs are ideal for large archives, too.

Additionally, wear-out isn’t an issue with SSDs. Those two node uplifts in the manufacturing process add literally years to the device life, and the economics of 3D NAND allow for extra over-provisioning, making the write life of the drive well beyond its time in a data center. This is especially true for archived storage, where writing is at a much lower rate.

There clearly is an inflexion point in the use of hard drives coming. Once parity is achieved, the transition to SSDs will become a tsunami. This transition is already well along for so-called enterprise drives. With price and capacity already matched or exceeded by SSDs, 7200 RPM and faster HDDs will quickly fall out of favor.

As in any transition, there will be points of resistance. After-market HDD spares will continue to be sold, though upgrades and replacements will increasingly use SSDs, especially in servers. The volume reductions in HDDs will probably lead to some major fire sales, though. These will all delay the day the last HDD ships, but do not expect a tape-like extended demise, with 30 years of predictions of the end of tape countered by ongoing increases in tape capacity. SSDs and HDDs basically do the same thing and there’s no reason to have both.

Speaking of tape, the SSD archive appliance likely will cause the demise of that hallowed medium. Today’s interest is more for rapid access to data, as demonstrated by Google’s Nearline cloud storage and Amazon Glacier. An SSD basis provides the desired low power with instant-on performance. Tape-based Glacier takes two hours to recover the first blocks of data.

Likewise, DVD-type archive storage will need a magic trick or two to remain in the race. A terabyte of DVDs will cost more than a terabyte SSD and that isn’t including the DVD library unit.

If you were told that a BMW and a golf-cart were the same price, which would you buy? That’s going to be the dilemma facing buyers sometime in 2016, with SSD and HDD. I think I know your answer!

PS: We may have a similar discussion in 2021, when ReRAM, PCM or some other solid-state solution, mounts a challenge to flash memory.