To my Experience, i will never prefer to have master server on a VM.
One of the worst scenarios is due to some storage issue all our Data stores are down and which made the Physical VM host to shutdown state and all VM machines are shutdown. Environment is completely down. There is situation where we need to verify the Data from recent backups, since our master is also VM, master server is also down and not able search for any data until Physical VM host is brought up and luckily Storage came up after 24 hours down time and we don’t need to recover any Data and even master is UP.
Second experience Master VM has shutdown abruptly and lost the connectivity Storage. Netbackup DB was corrupted due to some reason since it was abruptly shut down and second reason when master VM was brought up enough memory (16 GB prior) was not allocated. In this case I have recovered the entire catalog from Catalog backup tape.
