SandForce SF-2281 SSD Controller

SandForce introduces their new second generation solid state drives to both consumer and enterprise segments, with seven different models to choose from. On the consumer (retail) side you've got models using the older SATA 3Gb/s interface as well as the latest SATA 6Gb/s interface, while all enterprise drives utilize the 3rd-generation SATA 6Gb/s interface. More than any other factor, it's the Flash Channels/Byte Lanes configuration that these separate models. SandForce's SF-2000 series of SSDs continue to feature up to 8 data channels organized into 16 Byte lanes; similar to the previous generation of SF-1222/SF-1565 series SSD controllers, but now some models are scaled down for usage scenarios not requiring massive IO activity.

Previous SandForce SSDs utilized an over-provisioning technology, which allocated a portion of NAND for data storage and the remainder reserved for transaction and cache buffer space. Their latest controllers still use this technology, however SandForce claims that the 2200 series has a 0% minimum over-provisioning improvement, which could open up additional storage space if the remaining capacity made it necessary to complete a write cycle. Greater levels of over-provisioning are used by their SSDs built to sustain Enterprise duty cycles.

SandForce second-generation SF-2200 and SF-2100 SSD processors aren't just SATA 6Gb/s on paper - they actually require the bandwidth afforded to the host interface to deliver sustained sequential read/write performance up to 500 MB/s. SandForce DuraClass Technology is still a staple part of their feature set, but now include Trusted Computing Group (TCG) Opal-compliant Self Encrypting Drives (SEDs) support with AES-256/128 and double encryption. SF-2200 and SF-2100 SSDs also utilize high-speed ONFi2 and Toggle flash interfaces in single-level (SLC) and multi-level cell (MLC) NAND flash families from all major suppliers. The last major difference is the reduced minimum over-provisioning requirement, which continues to use an integrated buffer but returns more capacity for storage assignment.

Eight topside NAND flash modules sit in ranks behind the second-generation SandForce SF-2281 SSD processor, and plenty of electronics fill the remaining space in-between. Another benefit of SandForce's SF-2200 architecture is that all data recorded to the SSD remains on the NAND grid and removes the need for a separate cache buffer DRAM module. Once the SandForce SSD board is turned to expose the underside (image below), SandForce's efficient "DRAM-less" design features DuraClass technology to negate a separate memory buffer chip and enables a more flexible compact design. The result is a faster transaction, albeit at the expense of total storage capacity.

On second-generation SandForce-driven SSDs, a new SATA 6Gb/s SandForce SF-2281VB1-SDC processor is part of their SF-2200 family of retail SSD controller chips, although and identical SF-2181 processor exists for older SATA 3Gb/s connections. Offering 8 flash channels with 8 Byte lanes configured (one lane per channel), the SF-2281 maintains a BGA-256 package whereas the top-end SF-2282 delivers two lanes per channel on a BGA-400 package. More detail is available in our SandForce SF-2000 Series SSD Processor Overview article.

All SandForce SSD controllers offer native TRIM garbage collection in supporting Operating System (such as Microsoft Windows-7), Native Command Queuing (NCQ) with 32 command slots, and basic Self-Monitoring, Analysis, and Reporting Technology (SMART) command set. SandForce built the SF-2200 series to produce 500 MB/s Sequential Read and Write bandwidth with 60K (burst)/20K (sustained) IOPS Random Write (4K transfers).

The SF-2200 SSD processor provides enhanced ECC with BCH data protection, and also includes SandForce's unique RAISE (Redundant Array of Independent Silicon Elements) technology. RAISE provides the protection and reliability of RAID on a single SSD drive, thanks to flash architecture, without the significant write overhead of parity. The SandForce DuraClass technology automatically stores data using Trusted Computing Group (TCG) OPAL security with 256-bit AES encryption and automatic, line-rate double encryption with a drive-level password, preventing data extraction directly from the physical flash memory modules.

SandForce enables support for advanced 30nm- and 20nm-class NAND flash from all leading flash vendors with Asynch/ONFi1/ONFi2/Toggle interfaces with data transfer rates up to 166 Mega Transfers per second. Their latest generation of controllers also offers advanced ECC engine correcting up to 55 bits per 512-byte sector to assure high data integrity and support for future generations of flash memory. On the 120GB ADATA S511 SSD, sixteen multi-layer cell Intel 29F64G08AAMEI NAND flash modules are joined to the SandForce SF-2281 controller. Consumer-level SandForce SSDs generally allocate 7% capacity over-provisioning and 128GB devices will yield 120GB of usable storage space.

Because the SandForce SF-2200 SSD processor is a non-exclusive component available market-wide, Benchmark Reviews expects to see several new solid state storage products using this same controller in the very near future. Please continue on to the next section for details on this particular model, and performance SSD test results...

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