The reason behind the rising DRAM chip and module pricing was predictable by anyone who has followed the semiconductor industry for a decade or two. The last few years have been rocky for semiconductor memory vendors and whenever times are tough, these vendors know what to do to drive prices up: reduce capital expenditures, stop building memory fabs, and stop making so many memory chips. And that’s exactly what’s happened. It helps that in tight economic times, it’s relatively easy to forego the big capital expenditures needed to build new memory fabs or refit older fabs with new chip-making equipment.

DRAM Exchange provided a little fire to burn that coal in your stocking with the following heat-up-the-market predictions:

1. Capital expenditures for DRAM vendors will increase 80% year over year to US$7.85B from US$4.30B in 2009
2. DRAM aggregate demand will be slightly below aggregate supply in Q1 2010
3. DRAM pricing will fall appropriately 10% to 20% quarter over quarter in Q1 2010

DRAM Exchange also made the following predictions for DDR3 DRAM in the coming year:

1. DDR3 DRAM goes mainstream in Q1 2010
2. DDR3 DRAM market share will account for 60% and will likely reach 80% of commodity DRAM by 2H 2010
3. DDR3 DRAM prices will decline less than DDR2 DRAM prices given the strong platform migration momentum

Like Dickens’ ghosts of Christmas past, present, and future in “A Christmas Carol,” (go see the new movie!), these predictions from DRAM Exchange are merely shadows. Reality may or may not prove the predictions correct. Make your own decisions. TG Daily picked up DRAM Exchange’s predictions of a DRAM shortage for 2010 and one reader commented: “Prfft, they said the same thing last year.”

Why are the solid state disk drives still so expensive?

They are on the market for years and still so expensive. SSD of a reasonable capacity (256GB) costs as much as $800 or more. Aren’t they going to drop the prices?

Although the question appears to have been posed by someone not closely familiar with the ins and outs of hard-disk drive (HDD) and solid-state disk (SSD) technologies, markets, and pricing, it’s a frequent question posed by many in the industry. We’ve become so accustomed to large, regular drops in price/capacity for both mechanical storage (“rotating rust”) and semiconductor memory that we’ve collectively developed a sense of entitlement. If we can’t buy it today, we think, surely the price will drop and we’ll be able to afford it soon.

However, when we compare the price/capacity of SSDs against HDDs, we’re comparing one moving target against another. Moore’s Law governs the price of SSDs because the largest cost component in an SSD is NAND Flash memory (see below). Moore’s Law has been a monster force in the semiconductor industry, pushing prices ever lower for more than four decades. However, the HDD vendors are constantly working with their own price-reduction curve, which has proven to be just as robust as Moore’s Law. By pulling a veritable menagerie of rabbits out of various technological hats, HDD vendors have dropped per-bit pricing for HDDs about as fast as semiconductor vendors have cut the price/bit of NAND Flash memory.

Take a look at this graph from Handy’s keynote:

From the gross slopes of the two curves, you can see that HDD cost/capacity has remained about 20x lower than NAND Flash memory cost/capacity throughout this decade. Note that in 2006, there was a serious downturn in the slope of the curve for NAND Flash. Extrapolating that new slope led some to predict that NAND Flash cost/Gbyte would cross over that of HDDs by 2008 or 2009. That just didn’t happen. The increased rate of price decline was economically unsupportable and caused huge turmoil among NAND Flash vendors. (For extensive analysis of this situation, see this blog entry on Denali Software’s Web site.)

Now please understand, the expectation that NAND Flash cost/Gbyte would zoom past the HDD cost/Gbyte curve wasn’t just wishful thinking. NAND Flash per-bit costs did overtake and then zoom past that of DRAM, which was once the semiconductor industry’s king of cost/bit. That event happened in 2004 as shown in this slide from Handy’s keynote.

So the expectation that NAND Flash cost/bit would zoom past HDD cost/bit wasn’t at all far-fetched. It just didn’t happen. HDD vendors happily continued to cut the cost/bit of rotating storage, to the very great benefit of consumers and enterprise users everywhere.

Handy’s simple silicon anatomy of an SSD shows why the SSD’s cost/bit is closely tied to the cost of NAND Flash.

From a silicon perspective, Handy’s illustration shows 34 key semiconductor devices in his example 64-Gbyte SSD. Two of the devices are a controller chip and a DRAM buffer. Total cost for those two devices: $6. The other 32 devices are NAND Flash chips. Total cost for those devices: $64 for 64 Gbytes of storage (not counting spare capacity). The cost of the NAND Flash devices is more than 90% of the silicon cost of an SSD. The SSD’s price is largely set by the cost of its internal NAND Flash.

That’s why SSDs aren’t likely to replace HDDs for bulk storage in the foreseeable future. As long as the HDD industry has a road map leading to higher capacity and lower cost/bit storage, and it does, then the HDD will keep the throne as the storage capacity king.

SSDs can beat HDDs in raw performance by one or two orders of magnitude, as measured in IOPS. There’s nothing on the HDD road map that can change that situation. For applications that can measure the value of storage speed, and there are many such applications for enterprise-class storage, SSDs provide sufficient value to justify their higher price/bit. For most consumers, people who are selecting laptops for example, the choice between a 160-Gbyte HDD or a 32-Gbyte SSD for the same price is obvious. The consumer will choose more capacity (to store more music, more pictures, more video, and more movies) every time.

Now take a look at Handy’s curves for DRAM and NAND Flash cost/bit once again:

Note that the cost/bit of NAND Flash is now roughly 10% that of DRAM. That means that as a DRAM backup medium, NAND Flash doesn’t add that much to the cost of the DRAM it’s backing up. Unlike the comparison of NAND Flash and HDD capacity, which tilts far in favor of the HDD, NAND Flash densities are much better than DRAM bit densities and that gap is growing thanks to multi-level cell (MLC) storage. These economics are behind the idea for AgigA Tech’s AGIGARAM modules. For a small cost adder, volatile DRAM can be made bulletproof when paired with NAND Flash memory. For more detail regarding this idea, see the earlier 3-part series in this blog (here, here, and here).

The question’s not as simple as it seems. There’s a temporal quality to the question. What’s right ten years ago isn’t right today and probably won’t be right ten years from now. Semiconductor technology is both fluid and extremely dynamic. One thing’s certain. You need to deal with today’s problems today. If you can address the same problem in the same way two or three years from now, that’s great! But you still need to address today’s problem today. You need to use components you can get today, not some time in the future. The future may include some surprises that change today’s answer, but today’s answer must be based on what you can do today.

Why the emphasis on today? Well, any RAID server memory used today must be based on some sort of memory technology (or technologies) that’s commercially viable now. Researchers are working on more than a dozen new memory technologies that may someday produce a more ideal memory than the semiconductor memories we have at our fingertips today. It’s not clear when that might happen. Tantalizing technology announcements are made almost weekly. But technology announcements are generally light years away from being commercially competitive products and that’s never truer than when you’re talking about digital memory.

Bulletproof RAID server memory must have some mechanism to ride through power outages without data loss.  The previous two entries in this series (Part 1 and Part 2) discussed various approaches to creating bulletproof memory using battery-backed RAM. Seems like a great idea, but batteries aren’t particularly reliable in data-center environments where they live inside of heat-generating boxes squeezed into rack upon rack upon rack where they get no light and precious little maintenance. High-maintenance components like batteries just seem like a poor choice for creating memory that’s supposed to be bulletproof. Wouldn’t you agree?

So what’s that leave?

Well, you could use NAND Flash for memory rather than DRAM. NAND Flash devices have many excellent attributes. They do not require power to provide nonvolatile storage. They are currently the semiconductor industry’s cost-per-bit leader. NAND Flash chips available in higher capacities than DRAMs, which translates into more bits per same-size board, fewer devices per board for same-size capacity, or smaller boards depending on application needs. These are all great attributes.

Unfortunately, NAND Flash devices have some unhappy qualities as well. You can only write to them relatively slowly—much more slowly than DRAM. They also exhibit wearout failure, which is getting to be a bigger and bigger problem as lithographies shrink. NAND Flash devices are block oriented so you can’t write just one word. These three failings are major and make NAND Flash memories unsuitable for RAID server memories.

Unsuitable, that is, when used alone.

However, volatile DRAM paired with non-volatile NAND Flash make a pretty good team when it comes to building bulletproof RAID server memory. When the power’s good, use the DRAM like…well…DRAM. When there’s an indication that power’s about to fail, save the contents of the DRAM in NAND Flash devices.

Note that you can’t let the host CPU save the data when power’s already on the slippery downhill slope. You really don’t know how much time there is before the host CPU loses its mind. You need something more—bulletproof. You need a backup power supply that will sustain the memory subsystem during the data-backup operation and you need a local processor to oversee the transfer.

Batteries are still bad

The previous two installments of this series have already dealt with the many reasons that batteries are not suitable as the backup power supply. Barring the sudden invention of the Mr. Fusion portable reactor last seen attached to the back of Doc Brown’s DeLorean time machine in the Back to the Future movies, there’s really only one good alternative for emergency backup power for RAID server memories: ultra-capacitors.

Ultra-capacitors are capacitors that have electrodes with greatly expanded area, which result in greatly expanded capacitance. The electrode area expansion originates in porous carbon electrodes. Ultra-capacitors have capacities measured in Farads, much greater then conventional electrolytic capacitors. Although they require the proper care when designed into a backup power supply, ultra-capacitors can provide enough backup energy to support the emergency transfer of data from DRAM to NAND Flash memory in a bulletproof RAID server memory subsystem.

How practical is all this? Very practical. Take a look at the following graph, which plots projected memory costs in dollars per megabyte over the next few years. (This graph is based on iSuppli projections.)

As you can see, DRAM and NAND Flash are the least expensive semiconductor memories, per megabyte, and a megabyte of NAND Flash costs about one tenth of what a megabyte of DRAM costs. All of the leading “future” memories, which may someday replace DRAM, cost more. Some cost much more and they will continue to cost more into the foreseeable future. These “future” memory technologies are not about to replace DRAM today or tomorrow. They cost too much.

Finally note the dashed blue line. This line represents the per-bit cost of AGIGARAM, which fuses DRAM, NAND Flash, and ultra-capacitors to create the closest thing to a bulletproof RAID server memory that you can get today. Over time, the cost of a megabyte of AGIGARAM approaches the cost of the equivalent amounts of DRAM and NAND Flash added together. The cost of the memories will essentially dominate the other costs (controller, ultra-capacitor backup power source). Consequently, AGIGARAM, which is AgigA Tech’s bulletproof memory for RAID servers that’s available today, is not only the best technical approach to creating bulletproof memory, it’s the most cost-effective approach available today…and tomorrow.