Shared storage for dovecot cluster

[Gandalf Corvotempesta]

As I'm planning some server migrations and a new mail architecture,  i
would like to create an HA cluster

Any advice on which kind of shared storage should i use? Are gluster
performances with small files enough for dovecot? Any other solution?

It's mandatory to avoid any splibrains or similiar thus the replication
must be done on at least 3 storage servers.