Solid state drive (SSD) storage has begun to meet expectations for fast performance in a range of devices, from laptop PCs to smartphones. This adoption of solid state storage has also created high levels of optimism surrounding the potential for it to become the dominant form of storage, even overtaking hard–drive–based storage.
However, an objective look at the storage market does not support this. With the locality of where computing takes place shifting–analysts forecast that two thirds of compute devices will be phones and tablets by 2015–it will be increasingly difficult for flash chip manufacturers to serve all masters in any realistic and cost–effective way. It makes more sense to think of solid state as an enabling technology that can serve storage needs in mobile devices well and help get more performance out of the traditional hard disk storage used in laptops.
Comparing demand to production
Let’s look at some numbers. One exabyte of storage capacity equals one million terabytes, or one billion gigabytes. The total available market for laptop PC hard disk drives worldwide in 2010 was 69 exabytes and is forecast to grow to 95 exabytes in 2011.1 That’s a lot of storage capacity. What’s more, the average capacity of a notebook hard disk drive (HDD) is forecast to grow from nearly 300GB in 2010 to more that 359GB in 2011.1 Laptop users want more capacity, not less.
NAND flash memory is the storage component of SSDs. Conventional wisdom in some circles of the storage marketplace is that in the coming years SSDs will begin to replace HDDs in significant numbers in laptop PCs. However, keep in mind that in 2010 the entire NAND flash memory industry had enough installed capacity to produce just over 11 exabytes of storage. More than 10 exabytes (93%) of that went to consumer devices such as smartphones, tablets and SD cards.1 Just 0.86 exabytes (7%) of that NAND was used in SSDs.1
NAND flash memory production capacity is forecast to grow to 21 exabytes in 2011, with about 2 exabytes (9%) going to SSDs, the rest (91%) to smartphones and other consumer devices.1 The cost to build a megafab capable of producing 3.75 exabytes of non–volatile NAND flash memory is $10 billion.2 What’s more, a megafab—the minimum commitment for any significant increase in NAND production—would take two to three years to ramp up to full production. Smaller fabs would contribute little to meeting the enormous demand for laptop storage.
Can NAND flash makers keep up with laptop PC storage demand?
Assuming all of that additional NAND is used for solid state drives, that $10 billion2 investment would produce enough flash memory to serve just 4 percent of the 95–exabyte laptop storage market projected for 2011. Spending $10 billion2 to buy 4 percent of notebook storage market share, or $2 billion2 in revenue, is not viable.
To serve the entire laptop PC storage market in 2010, a $170 billion2 investment in NAND flash memory fabs would have been required. In 2011, a $250 billion2 fab investment would be needed to meet projected hard disk drive capacity demand for all laptops. But $10 billion2 is just for the cost of the fab. It doesn’t include the NAND, operations, fab depreciation and other significant costs.
Worldwide installed fab capacity is expected to grow from 11.5 exabytes in 2010 to 21 exabytes in 2011, a staggering 82%. But remember, just 9%, or about 2 exabytes, of that NAND will go to SSDs. Even at that impressive growth rate of more than 80 percent, with the vast majority of the NAND going to consumer devices, the yawning gulf between NAND flash memory production capacity for SSDs and demand for laptop storage will continue to widen.
Whatever portion of megafab production capacity is devoted to NAND flash for SSDs, the return on investment would be difficult to justify given the relatively small available market for laptop SSDs. Any additional capacity would be better justified to serve the market for smartphones, tablets and other consumer products for one chief reason: NAND makers can maintain much higher yields and lower prices for consumer–grade NAND because its performance and reliability specifications are much less stringent than the requirements for laptop PCs.
The upshot: Hard disk drives will serve the bulk of the laptop market for many years to come as makers of SSDs remain overstretched to meet ever–growing demand for laptop storage.
Solid state hybrid drives
Flash memory provides part of the answer to meeting the demand for performance in HDD–dominated laptop PCs, but SSDs can’t do it alone. And while the bulk of worldwide demand for NAND flash is for consumer products such as MPs players, cell phones and cameras, Seagate believes there is ample flash to support the opportunities Seagate sees for enterprise and hybrid solid state storage.
By integrating a small amount of flash into the hard drive, creating a solid state hybrid drive (SSHD), users get many of the performance benefits of flash technology without the added cost. Hybrid storage solutions apply intelligence to get the highest, most cost–effective performance from both solid state and hard drive technologies. In addition, when packaged in a 2.5– or 3.5–inch form factor and coupled with built–in intelligence, SSHDs provide the necessities of capacity, performance and price with the least amount of disruption to the user experience.
In addition to solving the challenge of how to gain cost–effective performance, SSHDs also help strengthen some weaknesses inherent to HDD and SSD devices to provide higher reliability from a hybrid solution.
Since hard drives contain a spinning disk, they are subject to mechanical wear-and- tear over time as well as having a lower shock tolerance compared to a flash drive. Hard drive manufacturers continue to push annualized failure rates (AFR) down and mean time between failures (MTBF) hours up, but guaranteeing reliability has its limits no matter the technology. SSHDs compensate for this by directing the storage of high–priority data to the SSD for both faster access and less vulnerability.
Solid state has its own problem with write cycles and data retention. Like a battery, SSDs gradually lose their ability to hold a charge (that is, retain data) with frequent use (erasures/writes). Wear leveling delays this phenomenon but fragments data and slows performance. And defragging to restore speed just adds disk wear. SSHDs help overcome this weakness by writing and erasing data that is not frequently accessed to the hard drive.
When it comes to hard drives, there will always be capacity growth, evolving interfaces and steady improvements in reliability, but what will begin to take center stage is the storage supplier’s ability to differentiate on performance. SSHD technology with intelligence designed–in is the natural path to enabling such differentiation.
Learn more about the innovation and products in Seagate's Solid State Hybrid Technology page.
1 Gartner, “Forecast: NAND Flash Supply and Demand, Worldwide, 1Q09-4Q11, 4Q10 Update,” page 2, Table 15-3, December 2010
2 All figures in USD