Introducing the Everest 2 Controller
Introducing the Everest 2 Controller
At its heart the Everest 2 controller is a 400Mhz dual core ARM based, multi-channel SATA 3 / 2 controller which features some very interesting technology, some of which bears more than a passing resemblance to SandForce’s key features. For example, SandForce has something called “DuraWrite” while the Everest 2 has “NDurance 2.0”. In its most basic form, NDurance 2.0 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 has had its abilities refined and upgraded in the new second generation Everest controller.
This life extension takes the form of various different techniques, the first of which is extremely advanced multi-level, BCH Error Correction Code. Much like the SandForce SF2281 controller makes use of 55 bits of ECC per 512 bytes of data, the Everest 2 has 128bits 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 Everest 2 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.
Advanced ECC is only one part of NDurance 2.0 equation and this controller also boasts Adaptive NAND Management and Signal Processing. ANM&SP means that it can apply both proprietary and vendor specific commands such as internal voltage shifting as well as sophisticated signal processing techniques during read, write and erase cycles. These cutting edge commands and techniques extend the life of the NAND cells by being more “gentle” on them (ie use less voltage) while creating less disturbance of adjacent cells during highly stressful processes. As a result, NDurance 2.0 minimizes the physical deterioration of the NAND and helps maximize the potential lifespan of all the NAND’s cells.
The last feature of NDurance 2.0 is an optional feature not enabled on the Vertex 4 called RNA. RNA is much like the SandForce SF2281’s RAISE (Redundant Array of Independent Silicon Elements) since it is a distributed data safeguarding technique very similar to those found in a RAID array. Much like your typical RAID array, the Everest 2 controller can automatically generate parity data for each block and then stripe this data across multiple NAND blocks. If one block suffers a catastrophic failure - above and beyond what the ECC can handle - the controller can still recover the data via this second layer of protection.
Also like SandForce SF2281 controller, the Everest 2 controller makes use of auto-encryption with 256bit AES support. It is unknown if this encryption is an optional feature or even if it is enabled on the Vertex 4 as this is an enterprise-centric item not required for the average home user or enthusiast.
While some features bear a striking resemblance to those included in SandForce controllers, the Everest 2 isn’t a copycat since it does some very basic things in radically different ways. The biggest difference is the fact that this controller doesn’t do any compression on the data before writing to the NAND. While OCZ states emphatically that the Everest 2 has greatly reduced write amplification they don’t explain exactly what the write amplification is beyond being low. In all likelihood it is higher than SandForce’s .6x, but OCZ is so sure of this controller’s abilities that - unlike the Vertex 3’s three year warranty- the Vertex 4 will come with a five year standard warranty.
By not first compressing the data, the Everest 2 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 MP3s or video. This directly impacts performance and in the case of the Everest 2 helps it attain an unheard of maximum rating of 120,000 IOP/s.
The other benefit to not compressing all data is there is no need for the massive over-provisioning which SandForce drives require. In the case of the Vertex 4 512GB model, this is 32GB of extra space you will have compared to a 480GB Vertex 3 drive. Of course, with zero over-provisioning, if enough NAND blocks die your drive will be in serious trouble as there will no “free” blocks to seamlessly take their place.
In addition to the aforementioned items the Everest 2 has another trick up its sleeve: its TLC NAND abilities. Triple Level Cell NAND is an interesting new technology which promises to make multi-Terabyte solid state drives not only a possibility but economically viable. TLC NAND is unproven and does come with a unique set of disadvantages but its inclusion does prove that the Everest 2 has been designed to work with as large and varied an array of NAND types as possible.
When taken as a whole the Everest 2 seems to be a capable high performance controller that’s more adaptable than any of its direct or indirect Indilinx predecessors.
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