Introducing the Barefoot 3 Controller
Introducing the Barefoot 3 Controller
Much like the Vector drive it is used in, the all new Barefoot 3 represents the culmination of over 10 years of engineering experience from OCZ and Indilinx. While there will invariably be a certain amount of comparison drawn between the Everest 2 controller and this new Barefoot 3, both controllers use entirely different designs. The Barefoot 3 represents a departure from previous philosophies. This is why the Vector is considered its own product line rather than being yet another Vertex, or as Alex Mei of OCZ stated “the solution was so differentiated that it warranted a new line positioned above our Vertex Series.”
Unlike previous controllers, the Barefoot 3 takes an entirely different approach to several key concepts. The largest of the changes is the actual design of the controller’s internal architecture. Instead of being one controller the Barefoot 3 is in fact two discrete designs combined on to one piece of silicon. This multi-core, multi-processor approach gives it a lot more overall power, flexibility and spare clock cycles than previous designs. This is also the main reason the Vector is able to boast such high sustained IO potential.
Most successful controller designs use multi-core ARM layouts that have proven to be both adaptable and relatively efficient. Using a multi-core design is nothing new as it allows for much better sustained performance with each core being able to be simultaneously handle different tasks. However, while the Barefoot 3 uses a multi-core Cortex ARM controller as its basis, it also contains a secondary OCZ Aragon unit as well.
When pressed for details regarding this combination, Daryl Lang and Alex Mei were willing to state that the “the purpose of the Aragon is to efficiently manage the interface to the flash devices”. In other words, unlike other controllers which simply dedicate one of the two processor cores to low level tasks, OCZ dedicates an entire 400mhz controller to it. This frees up the primary ARM controller for more time sensitive tasks.
Most controllers don’t have enough processor cycles to go around and designs usually conduct a delicate balancing act between garbage collection, other low level tasks and real time I/O requests. This is a big portion of what firmware refinement boils down to: modifying the amount of cycles the controller dedicates towards specific tasks. Compare and contrast the standard approach with OCZ new Barefoot 3: Rather than splitting cycles between various tasks, OCZ simply added in a second processing unit and added more cycles to spread out the load.
Like many modern designs, the Barefoot 3 uses an eight channel layout. However, unlike most which are 4CE designs, the Barefoot 3 can handle a whopping 8 chip enables per channel for a maximum of 64 NAND layers or twice what’s usually seen in competing solutions.
Interestingly enough, when pressed for types of NAND support OCZ stated there were “No current plans” for e-MLC / HET or TLC (Tri-Level Cell) NAND support stating “(the Barefoot 3) is targeted at the high end enthusiast market for client applications”, neither of which would be a good match for such clientele. This does narrow the types of NAND OCZ or other manufactures can use but both typical MLC NAND types - ONFi and Toggle Mode NAND- are supported. In all likelihood either e-MLC or TLC can be added via firmware updates if the need arises.
Much like the Everest 2 controller before it, the Barefoot 3 controller makes use of NDurance technology. In its most basic form, NDurance is an advanced NAND flash management suite designed to radically extend the life of the NAND cells and your data. NDurance first made an appearance in the Everest 1 controller, but since then it has had its abilities upgraded and further refined.
This life extension takes the form of various different techniques, the first of which is advanced multi-level, BCH Error Correction Code. In the Barefoot 3’s case, BCH has been set to 28bits worth of ECC per 1 Kilobyte of data. The controller’s progressive error correction capabilities are not fixed and can be adapted to the specific error characteristics of different NAND used in different runs, batches and even types. The end result is that the chances of your data being corrupted on any Barefoot 3 controller based drive –regardless of NAND type used - are greatly reduced as the ECC routines will be finely tuned to maximize data retention abilities of the NAND it is paired with.
The Barefoot 3 controller also has built in auto-encryption with 256-bit AES support. However much like the Vertex 4 and Agility 4 lineups, OCZ’s Vector doesn’t have this feature enabled by default. Auto encryption is not required for the average home user or enthusiast and it would have incurred a certain amount of performance loss due to the increased processing overhead. According to OCZ “This is something that we do turn on for enterprise specific drives. Vector does not have this turned on currently as this is not something that we felt really pertained to the targeted applications of this product, but we are continuing to evaluate enabling this functionality.”
The similarities in feature sets continue as the Barefoot 3 controller doesn’t do any data compression before writing to the NAND. By not first compressing the data, the Barefoot 3 boasts equally good performance for both compressible and incompressible data types. This is a major boon to consumers used to SandForce drives which incur a rather large performance penalty when dealing with already compressed data such as MP3 files or video.
Since data compression isn’t necessary the Vector series doesn’t require over provisioning in order to retain its performance over time so capacity will always be maximized. Of course, with zero over-provisioning, if enough NAND blocks get corrupted, your drive will be in serious trouble as there won’t be any “free” blocks to seamlessly take their place. OCZ emphatically state this controller has a low write amplification and the chances of enough NAND dying before the warranty expires is very low.
OCZ is so sure of this controller’s abilities they they’ve equipped the Vector with a comprehensive five year limited warranty. In a very interesting twist, OCZ also claim their drive is capable of 20GB of writes per day over the warranty’s lifespan. On first blush this may seem low for some environments but it is the same specification Intel uses for their SF2281 based 520 SSDs.
When taken as a whole the Barefoot 3 seems to be a capable high performance controller that’s more adaptable than any of its direct or indirect Indilinx predecessors. It certainly should make a great addition to OCZ’s current stable of high performance drives.
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