RAISE™ - Redundant Array of Independent Silicon Elements
RAISE™ improves total SSD reliability
While the next generation of NAND flash memories are being developed on smaller silicon geometries to reach higher densities, their endurance is significantly dropping. This is increasing the need for and importance of advanced data protection techniques to prevent data errors. LSI® SandForce® Flash Storage Processors (FSPs) feature a higher-level ECC to protect against correctable errors along with the innovative RAISE technology to provide protection against uncorrectable errors. This combination provides an uncorrectable bit error rate (UBER) of 10-29, with nearly one quadrillion times fewer uncorrectable errors than other controllers.
RAISE technology writes data across multiple flash die to enable recovery from a failure in a sector, page, or entire block. This is just like the concept of multi-drive RAID used in disk-based storage, however, RAISE only requires a single drive.
SSDs are built using flash die that are assembled up to 8 die per package. For optimum capacity, the SSD can be assembled with up to 16 packages. That puts 128 individual die in one SSD. If the failure rate (unrecoverable read error) of one MLC die is conservatively 1,000 PPM (a failure probability of 0.1%), then using the probability formula for 128 devices, the failure rate increases to 12.0% over the life of the SSD.
Using RAISE technology in an LSI SandForce Driven™ SSD 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.