by Woody Hutsell at www.appICU.com
In late 2006, Robin Harris at www.StorageMojo.com wrote “RAM-based SSDs are Toast –Yippie ki-yay”. As a leader of the largest RAM-based solid state storage vendor at the time, I can assure you that his message was not lost on me. In fact, we posted a response to Robin in “A Big SSD Vendor Begs to Differ” to which Robin famously responded “If I were TMS, I’d ask a couple of my better engineers to work part time on creative flash-based SSD architectures.” I cannot honestly remember the timing, but it is fair to say that the comment minimally reinforced our internal project to develop a system that relied heavily on SLC NAND Flash for most of its storage capacity. Within a few years, TMS had transitioned from a RAM-based SSD company to a company whose growth was driven primarily by Flash-based SSD. Nearly five years after the predicted death of RAM-based SSD I thought it would be interesting to evaluate the role of RAM SSD in the application acceleration market.
First off, it is important to note that RAM-based SSDs are not toast. In fact, a number of companies continue to promote RAM-based SSDs including my employer, ViON, who is still marketing, selling and supporting RAM-based SSDs. What may be more surprising is that the intervening years have actually seen a few new companies join the RAM-based SSD market. What all of these companies have identified is that there are still use cases for the high-performance per density available with RAM-based SSD. In particular, RAM-based SSDs continue to be ideal for database transaction logs, temporary segments or small to medium databases where the ability to scale transactions without sacrificing latency is critical. Customers in the e-commerce, financial and telecom markets will still use RAM SSD. When a customer says to me that they need to do be able to say they have done “everything possible” to make a database fast, I still point them to RAM SSD if the economics are reasonable. I think the RAM SSD business has promise for these specific use cases and will watch with curiosity the companies that try to expand the use cases to much higher capacities.
The second thing to note is that without RAM, Flash SSDs would not be all that appealing. You will probably all recall the reaction to initial Flash SSDs that had write performance slower than hard disk drives. How did the vendors solve this problem? Well for one thing they over-provisioned Flash so that writes don’t wait so much on erases. In enterprise solutions, however, the real solution is RAM. Because the NAND Flash media just needs a little bit of help, a small amount of RAM caching goes a long way toward decreasing write latencies and dramatically improving peak and sustainable write IOPS. This increases the cost and complexity of the Flash SSD but makes it infinitely more attractive to the application acceleration market.
Third, the companies with the most compelling Flash SSD performance characteristics have come out of the RAM SSD market. These companies had developed low latency, high bandwidth controllers and backplanes that were tuned for RAM. Contrast this with the difficulties the integrated storage manufacturers have had since their controllers and backplanes were tuned for hard disk drives.
Casual industry observers might ask a couple of other questions about this market:
- With the rapid decrease in RAM prices, is RAM likely to replace Flash as the storage media of choice for enterprise SSD? No.
- Are the large integrated storage companies likely to add a non-volatile RAM SSD tier in front of their new Flash SSD tier? I tend to doubt it, but would not rule it out completely.
- Aren’t customers that start with Flash going to look to RAM SSD to go even faster? I think some of these customers will want more speed but for most users Flash will be “good-enough”.
- Aren’t customers that start with RAM likely to move to Flash SSD on technology refreshes? Probably not. RAM SSD is addictive. Once you start with RAM SSD, it is hard to contemplate going slower.
To put this all in perspective, Flash SSDs did not kill the RAM SSD market. In some ways, Flash SSD and the big companies who have embraced it have added legitimacy to the RAM SSD market that it lacked for decades. I think RAM SSDs will continue to be an important niche in the overall application acceleration market and anticipate innovative companies introducing new use cases and products over the next five years.
To give credit where credit is due while Flash SSDs did not kill the RAM SSD market, it has come to dominate the enterprise storage landscape like no other technology since the advent of disk storage. Robin Harris may not have accurately predicted the end of RAM SSD but he was at the forefront of analysts and bloggers, including Zsolt at www.StorageSearch.com, predicting Flash SSD’s widespread success.