Data Backup Digest

There is no arguing the fact that solid state hard drives (SSDs) provide a vastly improved means of data storage than traditional, disk-based drives. Not only are overall drive speed and access times increased, but the technology maintains an increased level of data security and integrity when compared to older drives. Despite the advanced technology, there is room for improvement regarding the functionality of today's SSDs. Coincidentally, that's exactly what LSI is hoping to achieve with the recent introduction of their brand new SHIELD Error Correction Technology.

What is SHIELD Error Correction Technology?

Originally introduced at the Flash Memory Summit in Santa Clara, California, in August 2013, LSI SandForce's new SHIELD technology is a conglomeration of algorithms, procedures and routines that are meant to increase the lifespan and accuracy of the NAND flash memory used in SSDs today. It achieves this by providing several distinct processes.

The first process initiates a comprehensive error-checking algorithm. This is implemented by performing a parity check on every data request. This process, which is referred to as a hard low-density parity check, is backed up by five additional levels of soft low-density parity checking. Low-density parity checks have been used for quite a while in the telecommunications industry as well as in disk-based hard drives, so the technology has already proven itself effective in other mediums. As each individual check is employed, however, the latency, or overall data access time, increases slightly.

SHIELD's next process, referred to as RAISE, is similar to a full RAID architecture. Fully compatible with the current generation of LSI SandForce controllers, RAISE works in tandem with the hard and soft low-density parity checks to ensure the integrity and accuracy of the data on your drive. It does so at a cost, however, as the use of RAISE will increase data access latency by as much as 10 milliseconds. The RAISE process also uses additional processing power, though the exact amount has not been disclosed by LSI developers.

Finally, SHIELD employs a third process that locates, identifies and preserves data that has been recently accessed. This is used to guarantee prolonged accuracy and speedy recover times in the event of errors that may occur in the future.

Why is SHIELD Necessary?

LSI's SHIELD technology is a critical component to maintaining the future of SSDs for a number of reasons. Firstly, as Flash-based NAND memory expands to accommodate greater storage capacities, the need for a highly accurate error correction protocol is paramount. Additionally, SHIELD's functionality extends further to support advanced decoding strategies, improved noise handling methods and greater memory endurance than previous SSD standards.

Adaptive Code Rate

Another improvement over existing SSD technology, SHIELD's adaptive code rate algorithm lets the controller define the exact amount of bits used to maintain error-correcting code (ECC) memory. The adaptive code rate is then able to earmark additional bits as your Flash-based memory begins to degrade over time, while fresh NAND memory chips, which necessitate little to no error correction, can utilize these available bits to optimize drive performance and integrity.