Ok, from within the container, are you able to access /dev/md1? I suspect not, this seems like an issue with hardware.c and docker containers. Out of curiosity, are your running the container with --privileged, if not could you check if the issue behaves the same with this flag - this may explain why we haven’t seen this internally.
We collect stats on the device to monitor the devices health, this is warning that we are unable to resolve this device. It should be benign to Aerospike functionality. I’ll discuss this with the maintainers of hardware.c.