Kioxia FL6: PCIe 4.0 SSDs with fast XL flash and 60 DWPD

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Kioxia FL6: PCIe 4.0 SSDs with fast XL flash and 60 DWPD

Image: Kioxia

Kioxia is now bringing out its own SSD series that uses the SLC-NAND memory “XL-Flash”, which is trimmed for fast access. As a so-called storage class memory, the non-volatile memory is intended to fill the large gap between DRAM and conventional NAND in terms of performance and price. The FL6 series SSDs use PCIe 4.0.

XL-Flash is a storage class memory

Faster and more expensive than conventional NAND flash, but slower and cheaper than DRAM, the storage class memory can be roughly described as a further level in the storage hierarchy of computer systems. Intel and Micron have made it socially acceptable with the phase change memory 3D XPoint, which enables both SSDs with particularly low latency and high durability as well as a DRAM supplement in the DIMM form factor. Samsung’s Z-NAND, a high-performance SLC 3D NAND memory that is used in enterprise SSDs, is not quite as fast. Kioxia and Western Digital are pursuing a similar concept with the XL-Flash, which is called “extremely low-latency, high-performance flash memory“Is described.

  • XL Flash infographic

    Infographic for the XL-Flash (Image: Kioxia)

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    The XL-Flash is 3D-NAND (BiCS Flash), which is operated in SLC mode (1 bit per cell) and should only have a tenth of the latency when reading compared to normal TLC-NAND. Similarly, the IOPS should increase with random read and the performance with a small command queue (Queue Depth). Conventional NAND flash is usually internally divided into two or four memory areas, so-called planes, for more performance through parallel access. With the XL-Flash there are 16 plans instead. This reduces the distance between word and bit lines, which in turn ensures faster access times.

    The DapuStor H3900 enterprise SSD was one of the first products with XL Flash, but tests showed that Intel’s Optane SSDs with 3D XPoint are still far ahead in terms of latencies.

    FL6: Kioxia’s first SSD series with XL flash

    Only now is Kioxia, the flash partner of Western Digital, formerly known as Toshiba Memory, releasing its own SSDs with XL flash. It starts with the enterprise SSD series FL6, which in its 2.5-inch form factor presumably uses the PCIe 4.0 interface (dual-port compatible) and NVMe 1.4 with a U.3 connector. With the special flash memory, the SSDs available with storage capacities from 800 GB to 3.2 TB “excellent for latency-sensitive use cases such as caching layer, tiering and write logging“According to Kioxia.

    However, the press release still lacks key performance data: Neither the latency in reading and writing, nor the sequential throughput or the possible IOPS are mentioned. The editorial team asked Kioxia for more details.

    Kioxia FL6 SSD uses XL flash Kioxia FL6 SSD uses XL Flash (Image: Kioxia)

    The FL6 SSDs are specified with 60 Drive Writes Per Day (DWPD), which means that the SSD can be written to up to 60 times per day over the entire usable storage capacity within the scope of the guarantee (usually 5 years). Assuming 5 years, this would correspond to a total write volume (Total Bytes Written, TBW) of 87,600 TB for the 800 GB version up to 350,400 TB for the 3.2 TB model. Intel’s Optane P5800X with 3D XPoint storage is even designed for 100 DPWD, but so far only available with a maximum of 1.6 TB.

    Update 09/15/2021 10:36 a.m.

    While the editors are still waiting for an answer, Kioxia has elsewhere Called performance data. According to this, the FL6 series should achieve 6,200 MB / s in sequential reading and 5,800 MB / s in sequential writing. With random reading, 1.5 million IOPS should be possible with QD256. With random writing, there are up to 400,000 IOPS (but with QD32) in the data sheet. Kioxia specifies the latency for 4K access with QD1 as 29 µs reading and 8 µs writing. In view of previous statements, it is conceivable that the values ​​were swapped, because the latency should actually be much lower when reading.

    Kioxia FL6 specifications Kioxia FL6 specifications (Image: Kioxia (via Blocks and Files))

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