Stefan Mileschin

Toshiba has announced the fourth iteration of their OEM client NVMe SSD that is delivered as a single BGA chip package containing both the SSD controller and the NAND flash memory. The Toshiba BG4 is a significant upgrade over the BG3: Toshiba's new 96-layer 3D TLC replaces their 64-layer NAND, allowing for higher capacities and lower power consumption. The PCIe 3 x2 controller used in the BG2 and BG3 is replaced by a new controller supporting PCIe 3 x4, opening the door to much higher sequential I/O performance.

The BG4 is still a DRAMless SSD that relies on the NVMe Host Memory Buffer (HMB) feature to mitigate the performance penalties that a DRAMless drive otherwise suffers from. Toshiba has enhanced their use of HMB with the addition of parity checking for data the SSD stores in host DRAM, providing an extra layer of data protection even when the host system does not use ECC memory. The BG4's firmware has also been tweaked to expand the range of user data mapping information that can be cached in the host memory buffer, improving performance for use cases like copying large files. These changes mean that the BG4 will ask to use a larger chunk of host memory to accelerate its operation, but the requested HMB size is still less than 100MB. Other firmware changes have focused on improving random I/O performance and reducing the impact of background flash management on interactive performance. Preliminary performance numbers from Toshiba indicate that random write performance has almost doubled, and random read performance is well over twice as fast as the BG3.

https://www.anandtech.com/show/13814...th-96l-3d-nand