title: Cloudformation RDS Aurora : Invalid Storage Type
body: <p>Following is my CFD script to create an RDS instance.
  I am trying to create Amazon Aurora with PostgreSQL compatibility, but I am facing: <code>Invalid Storage Type : gp2</code> error.</p>
  
  <pre><code>  SnapshotRDSDBInstance:
      Type: AWS::RDS::DBInstance
      Properties:
        AllocatedStorage: 20
        DBInstanceClass: 'db.t3.medium'
        DBName: mydatabase
        StorageType: gp2
        Engine: aurora-postgresql
        PubliclyAccessible: true
        MultiAZ: false
        DBSubnetGroupName: !Ref SnapshotRDSDBSubnetGroup
        VPCSecurityGroups: 
          - !Ref SnapshotRDSDBSG
        MasterUsername: 'test'
        MasterUserPassword: 'Demo@123'
        BackupRetentionPeriod: 15
        DBInstanceIdentifier: 'myrds'
  </code></pre>
  
  <p>I also tried to remove the <code>StorageType</code> parameter in above script , but then I face <code>Invalid storage type: standard</code> error.
  I am not able to understand the root cause.
  I am using <code>ap-south-1</code> (Mumbai) region to launch this script.</p>