This is creating a lot of unnecessary confusion
Imho, and as a person in the field of hpc, lustre is still the most used filesystem in hpc systems worldwide. The mentioning of spectrumscale is an odd one, is spectrumscale is as old as lustre. Has no support in the kernel (doesnt need it) but is horribly expemsive. We are deploying clusters with lustre every week. The dev direction of lustre is to make builds that do not need specific kernels, but can use kernel modules to obtain its functionality.
Besides that, intel stopped its own offering if the fs, which was a specific patchlevel geared towards enterprise usage. This seemed to be a bit too far fetched even for intel. They still have the largest group of devs for lustre in house, they still offer l3 support and community support. In the field we encounter other filesystems, where 90 % is divided between lustre,BeeGFS and spectrumscale. The other 10% are the newcomers that grew up in the big data world. Scale out nfs is rare, as nfs does not provide support for large scale applications that need special offloaded I/O.
To call lustre down and out is way too premature. It has existed for most of its life without native kernel support, and with the latest efforts will not need that native support as it will be running by loaded modules.
This article is accurate to the point that the stubs in linux kernel are gone, but thats all.
Hdfs has no place in hpc. Unless its a hybrid system that offers best of both worlds, even then there is most likely both.
Just my 2 c