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 shift in devices used for computing – 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 achieve higher performance from the traditional hard disc 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 disc drives worldwide in 2010 was 69 exabytes and is forecast to grow to 95 exabytes in 2011.1 That is a lot of storage capacity. Futhermore, the average capacity of a notebook hard disc drive (HDD) is forecast to grow from nearly 300GB in 2010 to more than 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 two exabytes (9%) going to SSDs and the rest (91%) to smartphones and other consumer devices.1 The cost of building a megafab capable of producing 3.75 exabytes of non-volatile NAND flash memory is US$10 billion.2 Furthermore, 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 that all additional NAND is used for solid state drives, the US$10 billion2 investment would produce enough flash memory to serve just 4% of the 95-exabyte laptop storage market projected for 2011. Spending US$10 billion2 to buy 4% of notebook storage market share, or US$2 billion2 in revenue, is not viable.
To serve the entire laptop PC storage market in 2010, a US$170 billion2 investment in NAND flash memory fabs would have been required. In 2011, a US$250 billion2 fab investment would be needed to meet projected hard disc drive capacity demand for all laptops. But US$10 billion2 is just for the cost of the fab. It does not 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 two exabytes, of that NAND will go to SSDs. Even at that impressive growth rate of more than 80 per cent, 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 in serving 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 is that hard disc drives will serve the bulk of the laptop market for many years to come, as makers of SSDs will remain overstretched to meet the 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 cannot do it alone. And while the bulk of worldwide demand for NAND flash is for consumer products such as MP3 players, mobile phones and cameras, Seagate believes that there is ample flash to support the opportunities it 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 receive many of the performance benefits of flash technology without the added cost. Hybrid storage solutions apply intelligence to achieve 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 disc, they are subject to mechanical wear and tear over time as well as a lower shock tolerance compared to a flash drive. Hard drive manufacturers continue to reduce annual failure rates (AFR) and increase mean time between failures (MTBF), but guaranteeing reliability has its limits for any 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 hold a charge (retain data) with frequent use (erasures/writes). Wear levelling delays this phenomenon but fragments data and slows performance. And defragging to restore speed adds to disc 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 centre 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 on 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