preferredSubnetId

For MULTI_AZ_1 deployment types, it specifies the ID of the subnet where the preferred file server is located. Must be one of the two subnet IDs specified in SubnetIds property. Amazon FSx serves traffic from this subnet except in the event of a failover to the secondary file server.

For SINGLE_AZ_1 and SINGLE_AZ_2 deployment types, this value is the same as that for SubnetIDs. For more information, see Availability and durability: Single-AZ and Multi-AZ file systems.