RDS MySQL and MariaDB Increase Maximum Storage Size for R5 Instances
You can now create Amazon RDS for MySQL and Amazon RDS for MariaDB database instances with up to 64TB of storage when using R5 instance types. Previously, R5 instances supported 16TB of storage. The new storage limit is available when using the Provisioned IOPS (IO1) and General Purpose (GP2) storage types.
Source:: Amazon AWS