08-27-2019, 04:31 AM
https://www.tomshardware.com/news/toshib...40237.html
Quote:The company has also started research into Penta-level cell (PLC) NAND flash and actually verified working five-bit per cell NAND by modifying its current QLC NAND. The new flash provides more density with the ability to store five bits per cell, rather than just four in current QLC. But, to do this, the cell needs to be capable of storing 32 distinct voltage levels, and SSD controllers need to read them back accurately. With so many voltage levels to read to and write at nano-scale, the new technology is very challenging. To get control of the tighter thresholds, the company had to develop some additional processes that may adapt to its current TLC and QLC to boost performance.
QLC is already fairly slow and has lower endurance than other types of flash. PLC will have even less endurance and slower performance. New NVMe protocol features such as Zoned Namespaces (ZNS) should help mitigate some of the issues, however. ZNS by itself aims to reduced write amplification, reduce the need for media over-provisioning and internal controller DRAM usage, and of course, improve throughput and latency.