Why are SSDs Slow to Take Off?

Implications: Solid-state disk drive (SSD) makers are trying to break into small-capacity markets such as small laptops and enterprise servers.  There are too many manufacturers and they face significant issues to complete with magnetic hard disk drives (HDDs).

Analysis: SSD makers such as Micron, SanDisk, Stec, Toshiba, Samsung, and newcomer Intel are all trying to break into the storage market in a big way with NAND-flash based solid-state drives.

The drives have some advantages, especially for random access (because solid state drives have no mechanical "seek time" to access data), power consumption, and acoustic noise.  However, their peak data rates are much lower, and most importantly the cost per gigabyte is much higher.

SSDs have become dominant at the lowest capacity points in popular devices such as iPods and cell phones, but are still not competitive at higher capacity points.

Many assume that SSDs will inevitably become competitive, but they overlook the fact that HDD densities and costs per gigabyte continue to improve.  Also, the HDD industry has made large strides in reducing power consumption and acoustic noise. To make matters worse, advances in semiconductor density are reaching physical limits.  (For example, CMOS gate oxide thickness is now measurable in atoms.)  Major technical advances are needed to scale past 20 nm.  This implies that flash may not be able to keep up at higher capacities.

Flash memory has fundamental reliability limits that will directly impact their suitability for storage.  The flash cell undergoes long-term degradation and so has a fixed number of erase-write cycles before it stops working correctly.  Whether the industry can deal with this issue or whether SSDs will in fact have lower reliability remains to be seen.

Flash drives are considerably slower than HDDs for large sequential accesses.  This means, for example, that they cannot be used in DVR applications, and may be unsuitable for PC gamers if peak performance is needed.

Two companies bear close watch in this fray, Samsung and Seagate.

Samsung makes both NAND flash and hard disk drives.  While they are not industry leaders in HDDs, they continue to ship products, and the company will probably not allow different business units to compete directly.

HDD industry leader Seagate has made clear that they are working on solid-state drives.  Since they are not a semiconductor manufacturer, they will likely have to partner with someone like Intel.  However, their customer relationships and detailed knowledge of HDD interface specifications would probably be quite valuable for a company like Intel.  It will be interesting to see if they become serious players in SSDs, as it will directly impact their industry-leading position in HDDs.

It will be interesting to see how all this shakes out, but the long-term fundamental limitations of flash memory will likely constrain solid-state drives to the smallest capacity points for the foreseeable future.

And what about the smaller SSD players?  Unless they find a way to compete with flash-memory manufacturers, like Intel, and with tech-savvy HDD vendors, like Western Digital, they may have an uphill climb ahead of them.