OCZ Vertex 2 Pro, Sandforce Powered SSD Preview
The Vertex 2 Pro Series and Sandforce 1500
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OCZ Vertex 2 Pro Series 100GB SSD - click for full res
The real secret sauce of the Vertex 2 Pro can be seen under the hood. This SSD is comprised of 64Gb Micron NAND chips that operate at 166 MT/s. There are 16 of these chips on-board, 8 each on the top and bottom sides of the PCB. Other than the small 8-pin configuration EEPROM and one tiny 6-pin logic device, the Sandforce 1500 controller is the only other piece of pure CMOS silicon on board. The rest of the bill of materials consists of passive or electromechanical components (connectors etc). What really sets the Vertex 2 Pro apart from many current SSDs on the market is its Sandforce 1500 NAND Flash controller. Let's drop down for a look at this relatively new technology for SSDs.
Sandforce 1500 Series SSD Processor Block Diagram
That Sandforce 1500 series controller is a rather complex device and though we won't dive too deeply into the architecture, in consideration of your eyes possibly glossing over, we will point out a couple of key characteristics of Sandforce technology that sets it apart from other SSD NAND Flash controllers on the market. As you can see, this is a complex system on a chip of sorts that has a number of functional blocks beyond its Flash and SATA interfaces and processor core. Some of the microengines here that merit discussion are the DuraWrite and RAISE error correction blocks.
Intel claims their controller offers a 1.1X write amplification factor, while Sandforce claims their DuraWrite technology brings that down to .5X or less than half that of Intel. This also negates the need for on-board DRAM cache for a Sandforce-based SSD, because caching write data in order to alleviate amplification is no longer required. Finally, Sandforce claims that write endurance of an SSD based on their controller will have SLC-like endurance of up to 5 years, once again due to their proprietary technology that minimizes write amplification dramatically. We should also note that Sandforce-based SSDs like OCZ's Vertex 2 Pro that we're previewing for you here today, also support the TRIM functionality offered in Windows 7. Finally, you'll also note that there is an encryption engine block detailed in the block diagram above. Essentially, data is encrypted and decrypted on the fly, making it more secure from hackers, versus the simple password protection techniques on other SSDs. This engine, Sandforce reports, also completely offloads the host processor of any workload related to its security algorithm and we're sure is combined with some sort of compression algorithm (like Deflate for example) which also keeps data transfer rates up.
DuraWrite and AES 128 Encryption Technology -
"Write amplifcation" is a term that is used to describe what a typical SSD has to go through in order to write data to a drive. In general, the SSD has to read a 128K block of data into system memory, modify the content that needs to be written to that block and then write that entire 128K block back to the drive. This scenario holds true even for something as small as 4KB of data. This read-modify-write scenario takes its toll on the write endurance of the average SSD reducing its functional life dramatically. Typical write amplification for legacy SSDs has been in the neighborhood of up to 20X, which is a ton of wasted write operations and the reason why elaborate "garbage collection" algorithms have been developed to clean up data on SSDs after use so that they maintain performance.
Image courtesy: Sandforce, Inc.
RAISE Technology -
RAISE is an acroym that Sandforce coined that stands for "Redundant Array of Silicon Elements". Essentially, the technology, in combination with Sandforce error detection and correction (ECC) algorithms, combines RAID-like redundancy without the requirement of writing data twice to the drive. The company doesn't explain how this is achieved but they do go on to claim that "RAISE technology reduces the probability of a single unrecoverable read error by 100 times to 0.001%. Applying that same formula, the failure rate of the SSD drops from 12.0% to a mere 0.13%, nearly 100 times lower.
In short, though it's a bit of a mystery how they achieve this, once again with these proprietary technologies from Sandforce, MLC-based NAND Flash SSD reliability is increased by orders of magnitude supposedly. We'll touch on this again later...
