Samsung shows its first CNS SSD

With ZNS-SSD, the host controller takes care of many tasks that are traditionally done by the SSD itself. For example, it pre-sorts the data so that it can be written sequentially to individual zones of the SSD – this speeds up storage and ensures greater endurance. ZNS SSDs also do not require any flash reserve for over-provisioning; practically the entire capacity is available for applications. For a desktop PC, the CNS will not play a role in the foreseeable future; the advantages are particularly evident in large environments, i.e. in data centers. Western Digital is one of the leading companies in this relatively young technology, just six months ago the company presented the first suitable SSD. Another large SSD manufacturer is now following with Samsung: Samsung’s PM1731a will be available as a 2- and 4-TB model and exclusively in a 2.5-inch housing with a U.2 connector. Samsung plans to start mass production of the PM1731a in the second half of the year. The company has not yet publicly announced prices; However, this is also not common in the enterprise sector, where dozens or hundreds of such drives are often ordered. The Koreans are currently using TLC flash (3 bits per cell), but the more affordable 4-bit QLC memory will also be used in upcoming CNS SSDs.

Software support

ZNS-SSDs require a different control by the host system than usual PCIe-SSDs. Samsung submits to this xnmve.io provides a range of tools and documentation and, according to its own information, participates in Intel’s Storage Performance Development Kit. From working on Western Digital’s zoned storage initiative at zonedstorage.io is out of the question. It therefore remains unclear at first whether CNS SSDs from different manufacturers can later be easily interchanged with one another. The article gives further details about the CNS and the control of CNS SSDs SSDs rethought in c’t 6/2021. (ll)