Because UEK R5 adds support for NVMe subsystems and multipathing, enumerated device names that are generated by the kernel are not stable. This behavior is similar to the way other block devices are handled by the kernel. If you use enumerated kernel instance names to handle mounts in your fstab file, the mounts might fail or behave unpredictably.

Never use enumerated kernel instance names when referring to block devices. Instead, use the UUID, partition label, or file system label to refer to any block device, including an NVMe device. If you are uncertain of the device UUID or labels, use the blkid command to view this information.

Prior to multipathing, a subsystem number would typically map to the controller number. Therefore, you could assume that the subsystem at /dev/nvme0n1 was affiliated with the /dev/nvme0 controller. This correlation is no longer the case. For multipathing to be enabled, a subsystem could have multiple controllers. In this case, /dev/nvme0n1 could just as easily be affiliated with controllers at /dev/nvme1 and /dev/nvme2. Currently, no specific correlation between the subsystem device name and the controller device name exists.