Comment NAND is not taking over the data centre. Estimates of shipped disk and SSD capacity out to 2018 shows that, while flash will continue to grow faster, disk capacity will still outstrip that of flash by eight to one four years from now.

Total SSD capacity shipped is falling more and more behind disk

Analyst Stifel Nicolaus has estimated total capacity shipped in each category out to 2018, using its own and Gartner's estimates (see chart above).

Flash foundries cost $15bn and up, an amount that seems more in keeping with national infrastructure products than company manufacturing facility spend. For example, phase one of the UK’s HS2 high speed rail link between London and Birmingham was going to cost £16bn ($25bn) until it was revised up to £22bn ($34bn) in June last year.

No company is going to spend that unless it can see a sure-fire way to profit from it and, in a DRAM and NAND industry scarred by profit-killing gluts in the past, companies are going to be extra cautious.

The huge great problem is $/GB. New disk technologies such as shingling, TDMR and HAMR are upping areal density per platter and bringing down cost/GB faster than NAND technology can.

Each shrink in NAND geometry seems to require costlier manufacturing processes and more over-provisioning to keep endurance, expressed as drive writes/day for five years, up at acceptable levels. It’s obvious from the chart that 3D NAND, stacking cell layers on top of each other, isn’t going to drive up SSD capacity quickly enough, and cost/GB down fast enough, to be on a par with disk capacity growth.

Let’s do a quick back-of-the-envelope test and say that for SSD capacity to match disk by 2018 we would need roughly eight times more flash foundry capacity. Suppose that’s 20 foundries. It would mean an industry investment of $300bn, and that's just a very broad estimate. The real numbers are probably heading to and even past half a trillion dollars.

It ain’t going to happen. For data centre capacity storage disks rule, OK, and will carry on ruling until there's a solid state, semi-conductor manufacturing technology that is a hell of a lot cheaper than what we have now. ®