In my book Evolution of the Storage Brain, I make about 30 predictions of where I think the storage industry is headed over the next few decades. One of the more lively discussions these days is the future of the hard disk drive or HDD. HDD’s have been around for over a half-century, thanks to the work done by Rey Johnson and his team at IBM in producing the RAMAC 350 Disk Storage Unit in the 1950s. That very first disk drive, just like the ones being produced today, is comprised of 3 basic elements: rotating aluminum platters, magnetically coated surfaces, and moveable recording heads. Like all good technologies, the reason the HDD has survived so long is that nothing better has come along worthy of replacing it. During the 50+ year evolution of the HDD, components have become smaller while capacity has grown in incredible magnitudes. The RAMAC 350 literally required a forklift to move it, while today’s drives fit comfortably into the palm of your hand and store 1 million times more capacity than their ancestors.
While the HDD has had an amazing run, someday it will be replaced. Precision motors and actuators are subject to mechanical wear and will not perform indefinitely. Keeping drive platters spinning 24 hours a day but accessing data occasionally is an inefficient use of electrical energy. Finally, while HAMR (Heat Assisted Magnetic Recording) technology should take HDD capacities to 100TB and beyond, at some point the capacity and economic ceiling will be reached.
Currently, the only serious threat to the existence of HDD’s are an emerging class of Solid State Drives, or SSD’s. SSD’s were first build using DRAM but today largely depend upon NAND Flash modules. These devices emulate the look-and-feel of an HDD but since they are composed entirely of silicon, are not subject to the mechanical wear or the rotational latency delays suffered by HDD’s. SSD are growing in popularity but are still dwarfed in comparison to HDD shipments. There are two primary reasons why SSD sales are lagging – a) high costs and b) reliability concerns. On a cost per GB basis, SSD still commands a 10X price premium over HDD. From a reliability standpoint, the “flash” in Flash means that memory cells are weakened each time an electrical erasure is performed – which is required each time data is stored in Flash.
Flash vendors are tackling SSD reliability issues with sophisticated wear-leveling algorithms, and manufacturing economies of scale are driving costs down, but I just don’t think that Flash will be part of the long-term success of SSD’s. New technologies, such as Intel’s Phase-Change Memory or HP’s Memristor technology may prove to be a more viable option for SSD design.
So, while SSD vendors continue to reduce costs and improve reliability, HDD vendors will continue to chug along with a proven formula and ever-increasing capacities. I don’t expect to see a cross-over point occur between HDD and SSD for 10 years, or perhaps on 20 years at the most. There is certainty, however, that within 30 years the HDD is destined to be a relic and all data centers will house their data on solid-state devices.
While the slow transition from HDD to SSD takes place, an interesting phenomenon will occur. The marriage of HDD and SDD – the hybrid drive. Already produced by Seagate, Intel, and a handful of other companies, the Solid State Hybrid Drive, or SSHD, combines traditional rotating disk with a Flash-based front end cache. I forsee this technology being embraced by traditional IT shops within 5 years, but for a non-traditional reason – to enable disk spindown and energy savings. By front-ending traditional HDD’s with an intelligent cache, frequently accessed data can be staged in memory, allowing for the shutting down of mechanical components on the drive, except for occasional updates. The energy savings of SSHD and drive spindown will become very compelling as IT organizations become more energy conscious and data centers become modular in design – measured on the basis of performance per watt.
HDD’s transitioning to SSHD’s in 5-10 years before being entirely replaced by SSD’s within 10-20 years – that’s the way I see it…how about you?