What is Amazon RDS?

This page was generated from content adapted from the AWS Developer Guide

DB instances

DB instance classes

  • Note The DB instance classes that use the AWS Nitro System (db.m5, db.r5, db.t3) are throttled on combined read plus write workload.
  • Note When you perform operations with the AWS CLI, it automatically shows the supported DB instance classes for a specific DB engine, DB engine version, and AWS Region. Examples of the operations that you can perform include creating and modifying a DB instance.
  • Note To limit the output, these examples show results only for the General Purpose SSD (gp2) storage type. If necessary, you can change the storage type to General Purpose SSD (gp3), Provisioned IOPS (io1), or magnetic (standard) in the commands.
  • Note Each vCPU is a hyperthread of an Intel Xeon CPU core.
  • Note You can use AWS CloudTrail to monitor and audit changes to the process configuration of Amazon RDS for Oracle DB instances. For more information about using CloudTrail, see Monitoring Amazon RDS API calls in AWS CloudTrail.
  • Note When you modify a DB instance to configure the number of CPU cores or threads per core, there is a brief DB instance outage.

DB instance storage

  • Important When you modify an instance’s storage so that it goes from one volume to four volumes, or when you modify an instance using magnetic storage, Amazon RDS does not use the Elastic Volumes feature. Instead, Amazon RDS provisions new volumes and transparently moves the data from the old volume to the new volumes. This operation consumes a significant amount of IOPS and throughput of both the old and new volumes. Depending on the size of the volume and the amount of database workload present during the modification, this operation can consume a high amount of IOPS, significantly increase IO latency, and take several hours to complete, while the RDS instance remains in the Modifying state.
  • Note DB instances that use General Purpose SSD storage can experience much longer latency after read replica creation, Multi-AZ conversion, and DB snapshot restoration than instances that use Provisioned IOPS storage. If you need a DB instance with minimum latency after these operations, we recommend using Provisioned IOPS SSD storage.
  • Note General Purpose SSD gp3 storage is supported on Single-AZ and Multi-AZ DB instances, but isn't supported on Multi-AZ DB clusters. For more information, see Configuring and managing a Multi-AZ deployment and Multi-AZ DB cluster deployments.
  • Note For SQL Server, the maximum 64,000 IOPS is guaranteed only on Nitro-based instances that are on the m5*, m6i, r5*, r6i, and z1d instance types. Other instance types guarantee performance up to 32,000 IOPS. For Oracle, you can provision the maximum 256,000 IOPS only on the r5b instance type.
  • Important Depending on the instance class you're using, you might see lower IOPS performance than the maximum that you can provision with RDS. For specific information on IOPS performance for DB instance classes, see Amazon EBS–optimized instances in the Amazon EC2 User Guide. We recommend that you determine the maximum IOPS for the instance class before setting a Provisioned IOPS value for your DB instance.

Regions, Availability Zones, and Local Zones

  • Note For information about finding the Availability Zones for an AWS Region, see Describe your Availability Zones in the Amazon EC2 documentation.
  • Note Random selection of Availability Zones by RDS doesn't guarantee an even distribution of DB instances among Availability Zones within a single account or DB subnet group. You can request a specific AZ when you create or modify a Single-AZ instance, and you can use more-specific DB subnet groups for Multi-AZ instances. For more information, see Creating an Amazon RDS DB instance and Modifying an Amazon RDS DB instance.
  • Note A Local Zone can't be included in a Multi-AZ deployment.
  • Important Currently, the only AWS Local Zone where Amazon RDS is available is Los Angeles in the US West (Oregon) Region.