Since UEK R5 adds support for NVMe subsystems and multipathing, enumerated device names generated by the kernel are not stable. This is similar to the way that other block devices are handled by the kernel. If you use enumerated kernel instance names to handle mounts in your fstab, the mounts may 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 onto the controller number. Therefore, you could assume that the subsystem at /dev/nvme0n1 was affiliated with controller /dev/nvme0. This 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. There is no specific correlation between the subsystem device name and the controller device name.