Requirements and limitations for Amazon RDS Custom for SQL Server

Use the instance classes shown in DB instance class support for RDS Custom for SQL Server. The only storage types supported are solid state drives (SSD) of types gp2, gp3, io1, and io2 Block Express. The maximum storage limit for io1, gp2, and gp3 is 16 TiB while io2 supports 64 TiB.

Make sure that you have a symmetric encryption Amazon KMS key to create an RDS Custom DB instance. For more information, see Make sure that you have a symmetric encryption Amazon KMS key.

Make sure that you create an Amazon Identity and Access Management (IAM) role and instance profile. For more information, see Creating your IAM role and instance profile manually and Automated instance profile creation using the Amazon Web Services Management Console.

Make sure to supply a networking configuration that RDS Custom can use to access other Amazon Web Services services. For specific requirements, see Step 2: Configure networking, instance profile, and encryption.

The combined number of RDS Custom and Amazon RDS DB instances can't exceed your quota limit. For example, if your quota is 40 DB instances, you can have 20 RDS Custom for SQL Server DB instances and 20 Amazon RDS DB instances.

RDS Custom automatically creates an Amazon CloudTrail trail whose name begins with do-not-delete-rds-custom-. The RDS Custom support perimeter relies on the events from CloudTrail to determine whether your actions affect RDS Custom automation. RDS Custom creates the trail when you create your first DB instance. To use an already existing CloudTrail, contact Amazon Support. For more information, see Amazon CloudTrail.

You can't create read replicas in Amazon RDS for RDS Custom for SQL Server DB instances. However, you can configure high availability automatically with a Multi-AZ deployment. For more information, see Managing a Multi-AZ deployment for RDS Custom for SQL Server.

You can't modify the DB instance identifier of an existing RDS Custom for SQL Server DB instance.

For an RDS Custom for SQL Server DB instance that wasn't created with a custom engine version (CEV), changes to the Microsoft Windows operating system aren't guaranteed to persist. For example, you lose these changes when you initiate a snapshot or point-in-time restore operation. If the RDS Custom for SQL Server DB instance was created with a CEV, then those changes are persisted.

Not all options are supported. For example, when you create an RDS Custom for SQL Server DB instance, you can't do the following:

The maximum DB instance storage is 64 TiB.

You can't use RDS Proxy with RDS Custom for SQL Server.

You can't use the describe-reserved-db-instances API for RDS Custom for SQL Server DB instances.