Requirements and limitations for Amazon RDS Custom for SQL Server

Following, you can find a summary of the Amazon RDS Custom for SQL Server requirements and limitations for quick reference. Requirements and limitations also appear in the relevant sections.

Region and version availability

Feature availability and support varies across specific versions of each database engine, and across AWS Regions. For more information on version and Region availability of Amazon RDS with Amazon RDS Custom for SQL Server, see RDS Custom.

General requirements for RDS Custom for SQL Server

Make sure to follow these requirements 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, and io1. The maximum storage limit is 16 TiB.

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

• Make sure that you create an AWS Identity and Access Management (IAM) role and instance profile. For more information, see Creating your IAM role and instance profile manually.

• Make sure to supply a networking configuration that RDS Custom can use to access other AWS services. For specific requirements, see 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.

DB instance class support for RDS Custom for SQL Server

RDS Custom for SQL Server supports the DB instance classes shown in the following table.

SQL Server edition	RDS Custom support
Enterprise Edition	db.r5.xlarge–db.r5.24xlarge db.m5.xlarge–db.m5.24xlarge
Standard Edition	db.r5.large–db.r5.24xlarge db.m5.large–db.m5.24xlarge
Web Edition	db.r5.large–db.r5.4xlarge db.m5.large–db.m5.4xlarge

Limitations for RDS Custom for SQL Server

The following limitations apply to RDS Custom for SQL Server:

• You can't create read replicas in Amazon RDS for RDS Custom for SQL Server DB instances. However, you can configure high availability manually using Always On Availability Groups. For more information, see Working with high availability features for RDS Custom for SQL Server.

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

• You can't modify the server-level collation of an existing RDS Custom for SQL Server DB instance.

• Transparent Data Encryption (TDE) for database encryption isn't supported for RDS Custom for SQL Server. However, you can use KMS for storage-level encryption. For more information on using KMS with RDS Custom for SQL Server, see Make sure that you have a symmetric encryption AWS KMS key.

• 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 or C: drive aren't guaranteed to persist. For example, you will lose these changes when you scale compute or initiate a snapshot restore operation. If the RDS Custom for SQL Server DB instance was created with a CEV, then those changes are persisted.

• You can’t stop your RDS Custom for SQL Server DB instance or its underlying Amazon EC2 instance. Billing for an RDS Custom for SQL Server DB instance can't be stopped.

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

  • Change the number of CPU cores and threads per core on the DB instance class.

  • Turn on storage autoscaling.

  • Create a Multi-AZ deployment. However, you can configure high availability manually using Always On Availability Groups. For more information, see Working with high availability features for RDS Custom for SQL Server.

  • Configure Kerberos authentication using the AWS Management Console. However, you can configure Windows Authentication manually and use Kerberos.

  • Specify your own DB parameter group, option group, or character set.

  • Turn on Performance Insights.

  • Turn on automatic minor version upgrade.

• The maximum DB instance storage is 16 TiB.