RDS vs. EC2
RDS vs. EC2
4h 25m

This section of the AWS Certified Solutions Architect - Professional learning path introduces you to the AWS database services relevant to the SAP-C02 exam. We then understand the service options available and learn how to select and apply AWS database services to meet specific design scenarios relevant to the AWS Certified Solutions Architect - Professional exam. 

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Learning Objectives

  • Understand the various database services that can be used when building cloud solutions on AWS
  • Learn how to build databases using Amazon RDS, DynamoDB, Redshift, DocumentDB, Keyspaces, and QLDB
  • Learn how to create ElastiCache and Neptune clusters
  • Understand which AWS database service to choose based on your requirements
  • Discover how to use automation to deploy databases in AWS
  • Learn about data lakes and how to build a data lake in AWS

Hello, and welcome to this lecture, where I will discuss how to choose between using the Amazon Relational Database Service, or RDS, or Elastic Compute Cloud, or EC2 instances for your relational database deployments in the AWS Cloud. Both RDS and EC2 instances allow you to host databases securely within your own Virtual Private Cloud, or VPC. Both give you the ability to scale your databases to meet varying levels of storage, throughput, and performance demand, and both can be configured to operate within the AWS free tier. But that’s where the similarities end. In order to decide which option is best for your database, it helps to have a better understanding of the various benefits each approach has to offer. So let’s begin by discussing the advantages and disadvantages of both approaches, beginning with RDS.

Amazon RDS is an AWS-managed service that allows you to automatically install and provision relational databases in the AWS Cloud using popular open-source and commercial database engines including MySQL, MariaDB, PostgreSQL, and even Oracle and Microsoft SQL Server. RDS also offers Amazon Aurora, which is a MySQL and PostgreSQL-compatible database with up to 5 times the throughput of MySQL, up to 64 TB of auto-scaling SSD storage, and 6-way replication of your data across 3 availability zones, all at a fraction of the cost of a traditional database deployment.

Now what makes RDS appealing for so many use cases is just how simple it is to quickly spin up a new database without having to install or configure any operating systems or database software. And since AWS is fully responsible for the management of your RDS instance, you never have to worry about any of the administrative tasks typically associated with managing a database like configuring backups, security, or high availability. You also never need to worry about patching or hardening the underlying operating system of the servers that host your databases. This makes RDS ideally suited for smaller development shops or any organization that can’t afford the expense of a dedicated database administrator, or DBA function. And although you don’t have access to the server that hosts your RDS database, you can still use most standard database administration tools to connect to your database and perform any necessary actions.

So let’s quickly run through some of the other advantages of using RDS for your database deployments in the AWS Cloud. When you choose RDS, AWS will automatically provision your database instance along with its associated storage, configure automatic backups, and even automatic minor version upgrades if you choose.

RDS also takes care of encryption for your databases, both in transit and at rest. And when we talk about encryption at rest, this extends beyond just your primary instance storage and also includes your database backups and snapshots as well.

You even have the option to choose between preconfigured templates for production or dev/test deployments. So again, when you don’t have the time or resources for a dedicated DBA, or if you just want to get up and running as quickly as possible with your new database, it’s really great to let RDS handle all of these things for you.

And beyond all of this, many of the supported database engines in RDS will also allow you to configure a highly available multi-AZ deployment with just a single click. And with a multi-AZ deployment, you get a 99.95% uptime SLA. So in a multi-AZ deployment, RDS will automatically create a standby, synchronous replica instance in a different availability zone than your primary instance. RDS will then automatically fail over to that standby instance in the event an infrastructure failure is ever detected on your primary instance. And these failures could include anything from an outage within an availability zone, to a loss of network connectivity, or even a compute or storage failure. And best of all, when a failure does happen, AWS will automatically update the URL associated with your database to point to your standby instance during a failover, then back to your primary instance once it’s up and running again. And all of this happens without requiring any manual intervention from an administrator whatsoever.

Now when it comes to scalability, RDS makes it easy to scale out your database deployments by adding asynchronous read replica instances, which can help offload read demand from your primary instance. And you can imagine how much time and effort would be involved for a DBA to have to spin up additional EC2 instances and then configure a solution like database mirroring or a failover cluster, so RDS definitely offers some advantages when it comes to configuring high availability and scalability. To learn more about when to use Multi-AZ deployments and read replicas with RDS, please check out this course:

And to create your first RDS database, check out this hands-on lab:

So as you’ve seen, RDS offers a lot of inherent advantages. It’s extremely easy to set up, it’s cost effective, and it offloads the responsibility for your more time and labor-intensive database administration tasks to AWS, allowing you to focus on your own business requirements. But there are still scenarios where it makes more sense to leverage EC2 instances to host your relational databases instead of RDS. So now, let’s talk about some of the reasons why you may want to choose EC2 instances over RDS.

Amazon EC2 allows you to provision virtual servers on demand that can run a variety of different operating system types and versions, whereas RDS abstracts away the underlying operating system of the database instance. So if your application requires a specific OS type or version for your database, or if you need to run a database that isn’t currently supported by RDS such as IBM DB2 or SAP HANA, you’ll need to provision your own EC2 instances. You’ll also need to use EC2 instances if your application requires you to configure any operating system-specific settings, or install any additional software directly on your database server.

It might also make sense for you to leverage EC2 instances if your organization already has full-time DBAs on staff who need to have access to advanced features and configuration settings within the database. For instance, RDS doesn’t support some of the more advanced features in Microsoft SQL Server such as persistent memory devices or its Resource Governor. If your application requires any of these features, you’ll have no choice but to provision SQL Server on an EC2 instance.

So as you’ve seen, most of the reasons you’d want to choose EC2 instances over RDS involve needing to have a greater level of control over your database or the underlying server operating system than what RDS provides. And this could involve anything from controlling exactly when or how you apply patches and perform maintenance on your database, to which ports and protocols you want your database to use. Perhaps you need to configure multiple versions or multiple instances of a particular database engine on a single server. You may even need to set up an advanced RAID and striping configuration for your database’s storage using EBS volumes. While all of these would be non-starters with RDS, they’re entirely possible when using EC2 instances.

Now just because you choose to use EC2 instances instead of RDS doesn’t mean you can’t still configure some of the native functionality that RDS provides such as high availability, automatic failover, and scheduled backups for your databases. Just know that setting all of this up with EC2 instances will require significantly more effort than if you just used RDS. But depending on your specific requirements, this may be a worthwhile tradeoff for you.

So that covers the reasons you might want to use EC2 instances for your database deployments instead of RDS. To create your first EC2 instance, please check out these hands-on labs:

So to wrap things up here, you’re probably wondering: with all the benefits that RDS has to offer, surely all of this added functionality comes at a much higher cost when compared to just running your database on EC2 instances. Surprisingly, though, costs for database deployments using RDS and EC2 may be more comparable than you might expect. While RDS deployments are typically more expensive than comparable EC2 instance deployments, the difference in cost will vary depending on the specific instance and storage types you choose for your deployments. It’s also important to remember that the additional costs associated with those manual database administration tasks will become your responsibility if you choose to use EC2 instances instead of RDS.

So if you’re interested in getting a better sense of what these various database deployment options might cost for your applications in the AWS Cloud, you can input your specific numbers into the AWS Pricing Calculator at, where you can configure pricing estimates for different types of deployments by searching for things like RDS, Oracle, or EC2.

And just a couple of final thoughts: if you already have a dedicated DBA on staff, you’ll probably want to use EC2 instances for the cost savings you’ll get compared to RDS. You’ll also want to use EC2 instances if you need to provision a database type or version that isn’t supported by RDS. But in many other cases, RDS will probably be your best option. By reducing the management overhead associated with running your relational databases in the AWS Cloud, RDS allows you to worry less about tedious, labor-intensive administrative tasks, enabling you to focus on the things that deliver value to your business instead.

About the Author
Learning Paths

Danny has over 20 years of IT experience as a software developer, cloud engineer, and technical trainer. After attending a conference on cloud computing in 2009, he knew he wanted to build his career around what was still a very new, emerging technology at the time — and share this transformational knowledge with others. He has spoken to IT professional audiences at local, regional, and national user groups and conferences. He has delivered in-person classroom and virtual training, interactive webinars, and authored video training courses covering many different technologies, including Amazon Web Services. He currently has six active AWS certifications, including certifications at the Professional and Specialty level.