MySQL datafiles on SMB3 network storage We have MySQL-server on Ubuntu with InnoDB-datafiles on a local disk. As part of an upgrade program, the company is planning to put the datafiles on a Windows fileserver where they can be mounted with SMB3.

Is it a good idea to put the InnoDB-files on a network share or is it better to keep them on a local disk?
NO!  MySQL is not designed to allow two servers to access the same databases.

Or, maybe...

If your goal is to provide redundancy for the case of server failure, then maybe you could set up a non-running MySQL on a secondary server, ready to mount the disk subsystem in the case of failure.

Consider, instead, Clustering (Galera, PXC, InnoDB Cluster).