Last week I highlighted a pair of ARM processors with very different use cases, and now the pattern repeats as Western Digital, a company synonymous with hard-disk technology, introduces a pair of SSDs for markedly different use.\nThe Western Digital Ultrastar DC SN630 NVMe SSD and the Western Digital CL SN720 NVMe SSD both sport internally developed controller and firmware architectures, 64-layer 3D NAND technology and a NVMe interface, but that\u2019s about where they end.\n\nThe SN630 is a read-intensive drive capable of two disk writes per day, which means it has the performance to write the full capacity of the drive two times per day. So a 1TB version can write up two 2TB per day. But these drives are smaller capacity, as WD traded capacity for endurance.\nThe SN720 is a boot device optimized for edge servers and hyperscale cloud with a lot more sequential performance. Random write of the SN630 is over 10x the speed of the SN630720, and SN630 is better optimized for fast random writes.\nBoth use NVMe, which is predicted to replace the ageing SATA interface. SATA was first developed around the turn of the century as a replacement for the IDE interface and has its legacy in hard disk technology. It is the single biggest bottleneck in SSD performance.\nNVMe uses the much faster PCI Express protocol, which is much more parallel and has better error recovery. Rather than squeeze any more life out of SATA, the industry is moving to NVMe in a big way at the expense of SATA. IDC predicts SATA product sales peaked in 2017 at around $5 billion and are headed to $1 billion by 2022. PCIe-based drives, on the other hand, will skyrocket from around $3.5 billion in 2017 to almost $20 billion by 2022.\nSo the new SSDs are replacement not only for older 15k RPM hard disks but SATA drives as well with specific use cases.\n\u201cThe data landscape is rapidly changing. More devices are coming online and IoT is trying to connect everything together. The world is moving from on-prem to the cloud but also from the core cloud to the edge,\u201d said Clint Ludeman, senior manager for product marketing for data center devices at Western Digital.\nReducing latency is becoming an issue, whether it\u2019s a roundtrip from device to data center and back again or reducing latency at the core of the data center. \u201cBig Data opens up opportunities, but then you gotta do something with data. Fast SSDs allow you to do something with the data,\u201d he said.\nThat\u2019s where the targeted products come into play. \u201cWe do see a shift from traditional server architecture, where an OEM would throw a server out there and not know what was running on it. Now we\u2019re seeing a case where customers know their workloads and know their bottlenecks. That\u2019s how we\u2019re designing purpose-built products. As software stacks mature, you see different bottlenecks. It\u2019s a continual thing we\u2019re chasing,\u201d he said.\nAnd by going to NVMe they are able to reduce latency in the software stack to microseconds rather than the milliseconds that a hard disk works on. \u201cWe would have performance bottlenecks you couldn\u2019t unlock with SATA or SAS interfaces. Now we can do real-time computing,\u201d said Ludeman.\nThe CL SN720 is shipping now. The Ultrastar DC SN630 SSD is currently sampling with select customers with broad availability expected in April.