Firmware as the performance differentiator for SSD controllers

Anandtech has just posted a meaty article about SandForce SSD controllers as used in SSDs from OCZ and Corsair. (Understanding SandForce's SF-1200 & SF-1500, Not All Drives are Equal) It’s worth a read from at least two perspectives. First, it gives you some pretty deep insight into the real importance and value of the firmware running on these SSD controllers. As the Anandtech article discusses, controller firmware can make a substantial performance difference using the same hardware. In the case of the SandForce SF-1500 enterprise SSD controller and the company’s SF-1200 “client” SSD controller chips, firmware makes all the difference in performance because the two devices are electrically the same IC. Both chips running their associated firmware are rated at 30K random-read IOPS (I/O operations per second for 4-Kbyte reads) but the SF1500 is rated at 30K random-write IOPS (4-Kbyte writes) while the SF-1200 is rated at 10K random-write IOPS, which is a whopping two-thirds less performance than delivered by the electrically identical SF-1500 controller chip. There’s also an order-of-magnitude difference in rated data reliability between the two controllers, which you’d expect customers to want for enterprise-class SSDs. From the perspective of product positioning, this performance spread makes tremendous sense because the enterprise-class SF-1500 is reported to be substantially more expensive than the SF-1200 and the price premium is largely attributable to the differential speed and data-reliability performance delivered by the controller firmware (along with some extra reliability testing for the SF-1500 chip).

As Anandtech reports, because of a special relationship with SandForce, OCZ apparently got a special “fast” version of the control firmware for the SF-1200 controller that delivers the faster random-write IOPS performance of the SF-1500 and OCZ will reportedly be using that controller-chip/firmware combo in an upcoming Vertex 2 SSD. Anandtech further reports that this “fast” SF-1200 firmware reached at least one other SSD vendor, Corsair, through an early firmware release. Anandtech has tested an early review version of this drive and it delivers the higher performance. A later production version of this controller firmware apparently does throttle the SF-1200’s write IOPS performance to the rated “client”
SSD levels.

Despite Anandtech’s stated concerns, all this versioning and throttling isn’t anything particularly new or insidious in the electronics industry. The end customer pays for performance, which is both a real and perceived value, whether or not the performance is due to hardware or firmware differences. From an SSD customer’s perspective, it’s the drive delivering this performance and most customers will not care or even understand the fine distinction between hardware-delivered and firmware-delivered performance. In fact the Anandtech article notes that Intel does a similar thing by enabling or disabling Hyperthreading on two differently priced Core i5 and Core i7 processors. Same die, different performance. I know of a case all the way back in the 1970s where changing one bit in a product’s firmware image doubled the amount of RAM available to the user. Changing that bit cost the customer a few thousand dollars. So the practice isn’t new. But SSD vendors do need to know the difference. They need to understand the cost/performance tradeoffs they are making, because their products’ performance will reflect the consequences of these choices.

Thus the point of this blog entry is to point out, perhaps even to underscore, that firmware is a big differentiator in SSD performance, just as it is in just about any product category. SSD vendors need to understand this. Companies developing SSD controller chips should be aware that excellent controller firmware can substantially differentiate products, just as it has for SandForce’s SF-1500 and SF-1200 controllers. SSD manufacturers should be ready to grill their controller vendors about the supplied firmware. Is it as good as it can be? Could it be faster? Very good questions to ask as the SSD competitive landscape continues to heat up. SSD controller-chip vendors: be prepared.