Healthy debate is often necessary to get a balanced view of an emerging technology. Somewhere between endorsements and detractions, a realistic understanding of the long-term outlook for a technology arrives. As such, I have decided to turn to a guest once again for the second installment in what I hope to be an ongoing debate over the merits of flash SSDs (solid-state drives).

For those who missed the first installment, I spoke with Joel Hagberg of Fujitsu, who questioned the long-term outlook for flash SSDs, pointing out that the much-hyped advantages of SSDs over CSDs (conventional spinning drives) -- better performance, improved reliability, and lower power consumption -- may very well be too minimal to justify the price.

This week I turn to Scott Nelson, vice president of the memory business unit at Toshiba America Electronic Components and Semiconductors, for insights on the pro-SSD side.

In our conversation, Nelson touched on several of the points Toshiba published in a recent Web document disputing what the company considers the most common misrepresentations of the technology.

First off, according to Nelson, the current 56nm flash memory format has yet to reach its full potential. By Toshiba's estimates, performance for this format should double to 200MBps for reads and 80MBps for writes. And that doesn't touch on what is in store for future generations, Nelson says.

By year's end, Nelson believes we will see the flash memory format shrink to 43nm, yielding performance that will reach 240MBps for both reads and writes. Fast-forward to 2010, and the footprint will shrink even more, well below 40nm, according to Nelson, bringing performance in excess of 400MBps, again for both reads and writes, which will exceed what SATA 2 can sustain, thus requiring the adoption of SATA 3 as a host interface for SSDs.

As the shrinking footprint might suggest, mobile devices will benefit most from these jumps in performance, Nelson says. As for Toshiba, it is betting high on MLC (multilevel cell) flash memory for laptops, which promises to be less expensive and denser, while providing more capacity than SLC (single-level cell) flash.

If those two acronyms are foreign to you, the quick take is that SLC stores a single bit per cell, whereas MLC packs two or more bits in every cell. As such, assuming similar form factors, MLC packs more data in the same space.

But if MLC is best for notebooks, where will SLC flash find its ultimate home? Nelson answers before I can voice that question: "SLC-based drives, that technology is very important for the enterprise, where they need the higher performance and the higher reliability."

Not surprisingly, Toshiba plans to enter the nascent SLC SSD space. Although Nelson did say this foray will begin in 2009, he would not reveal details regarding the capacity and performance of those upcoming enterprise drives.

Overall, Nelson believes the demand for SSDs is on the rise. But although Toshiba expects customers will buy more laptops with MLC-based SSDs going forward, Nelson admitted that that number will likely remain a small fraction of the total number of laptops sold.