On August 10, 2017, the Flash Memory Summit ended in Santa Clara, California, where mass storage and semiconductor manufacturers presented new flash products. Market analysts at Gartner expect SSDs to grow by 20% per year in the mainstream PC market over the period from 2016 to 2021. This shows that the replacement of rotating hard disks is progressing rapidly.

One bit more per cell

At chip level, Western Digital announced its X4 technology for the BiCS 3D NAND memory architecture. BiCS stands for Bit Column Stacked and is Toshiba's 3D manufacturing process for flash memory, which has been in production since 2015. BiCS3 devices with 64 layers are currently being manufactured. Western Digital is now expanding the storage capacity of these components by storing not just three bits per memory cell (triple level cell) but four bits (X4 or quad level cell). This means that a single flash chip can store 768 Gbit. The corresponding drives in M.2 and 2.5-inch design with capacities from 256 GB to 2 TB are already available in Western Digital's online store, but cannot yet be ordered. Availability: "Summer 2017". Western Digital has also already announced the use of X4 technology for the next BiCS generation, BiCS4 with 96 layers. However, a date has not yet been given - the new chips are not expected to be available this year.

Western Digital makes no statement about the longevity of the X4 memory cells. After all, the controller must be able to reliably distinguish between 16 different voltage levels for the four bits per cell. The switch from two to three bits per cell already resulted in a significant drop in possible write cycles: from approx. 10,000 to 1,500. However, 3D flash memory is manufactured with larger structure widths than planar flash memory. This makes the cell more robust. Toshiba assumes that the durability of quad-level cells is almost as long as that of triple-level cells.

New consumer and server SSDs from Toshiba

So far, however, Toshiba itself has stuck with TLC technology. The SG6 SSD series presented at the Flash Memory Summit uses the current BiCS components with 64 layers. The SSDs are available in capacities of 256, 512 and 1024 GB and are intended for mainstream PCs. The data transfer rate reaches up to 550 MB/s for writing and 535 MB/s for sequential reading. This product generation is also currently only available "for selected customers". The storage devices, which are available in M.2 and 2.5-inch format, will not be available in stores until later in the year.

Toshiba has also introduced the SSD generations PM5 with SAS interface and CM5 with NVMe connection based on the BiCS3 chip generation for corporate customers and installation in servers. The PM5 series is available with storage capacities of up to 30.72 TB in a 2.5-inch form factor. Thanks to multi-link SAS, the sequential write and read speeds are up to 2720 MB/s and 3350 MB/s respectively. The CM5 series is equipped with an NVMe interface (Non-volatile Memory Express), a modification of PCI Express. The maximum possible capacity in the 2.5-inch housing is "only" 15.36 TB.

NGSFF: New design for server SSDs

At Samsung, the 3D flash memory chips are called "V-NAND" - Vertical NAND. In 2018, Samsung plans to introduce a V-NAND chip with a capacity of 1 Tbit. By stacking 16 such chips in one housing, a 2 TB module is to be created in a single package.

For server applications, Samsung is sampling an SSD with 16 TB in NGSFF format. At 30.5 x 110 x 4.38 mm³, this design is similar to the maximum size of M.2 and allows a storage density of up to 576 TB in a 1U server based on the 16 TB product generation. The NGSFF design was developed by Intel to build rack servers with a storage capacity of one petabyte, which would probably be possible with the next generation of memory chips. Samsung wants to work with industry partners to standardize the NGSFF format. The first NGSFF product is expected to be launched in the fourth quarter of 2017.

Controller for industrial flash memory

While server SSDs require maximum capacities and transfer rates, industrial applications depend on durability and reliability. Controller manufacturer Hyperstone from Constance on Lake Constance, for example, takes care of these aspects. The new F9 flash controller for CompactFlash contains "hyReability" functions for long-term data retention and precautionary measures against data loss in the event of a power supply failure. Although the CompactFlash memory card format has been superseded by SD cards in the end customer segment, it is still used for some professional digital cameras and in industry. The F9 controller supports write rates of up to 120 MB/s and random writing with up to 4000 IOs per second. It can control SLC, pSLC, MLC and 3D NAND devices. A secure boot function protects against unauthorized firmware changes. The ultra-low alpha package reduces soft errors caused by alpha radiation. The controller operates in an extended temperature range of -40 to +85 °C.

Data protection in the event of a power failure is also the purpose of the "PowerGuard" function that Spectra offers on its M336 series SSD drives. Capacitors, which are constantly charged during regular operation, ensure that write processes are still completed in the event of a power failure. The storage devices are available in 2.5-inch format with 32 to 512 GB and as mSATA modules in three versions of 32, 64 and 128 GB.