Getting More Life out of MLC with Controller Technology July 12, 2012,
Volume 173, Issue 2
George Crump of Storage Switzerland and Scott Switzer of STEC conduct a YouTube deep dive on MLC SSD Reliability that shows how controller technology can be used to make MLC SSD devices more reliable and enterprise ready. The presentation begins with the cost differential between SLC and MLC, which gives the nod to MLC for providing twice the capacity for the same cost as SLC. Considering durability, however, SLC's cycle life is in the range of 100K while MLC cycle life is typically 5000 cycles, though Switzer notes that the EMLC results in cycle life of something like 30K cycles. The write-rate of the EMLC is slowed, however, in order to attain this level of durability. The average duty cycle in enterprise systems tends to favor the SLC, however, while the MLC and EMLC are better suited to the consumer market. STEC has extended the cycle life of MLC technology through "cell care" to something in the neighborhood of 60K cycles. The key to this extension is the controller, Switzer maintains, which STEC had designed to talk to the inside of the FLASH chip through multiple channels that enable higher throughput rates. STEC employes fine grained control of individual cells that economizeS the erase-write-read activity, thereby lengthening cell life.