This blog post will give a brief overview of Amazon RDS capabilities and limitations, and how Percona Support can help you succeed in your Amazon RDS deployments.
One of the common questions that we get from customers and prospective customers is about Percona Support with Amazon RDS. As many companies have shifted to the cloud, or are considering how to do so, it’s natural to try to understand the limitations inherent in different deployment strategies.
Why Use Amazon RDS?
As more companies move to using the cloud, we’ve seen a shift towards work models in technical teams that require software developers to take on more operational duties than they have traditionally. This makes it essential to abstract infrastructure so it can be interacted with as code, whether through automation or APIs. Amazon RDS presents a compelling DBaaS product with significant flexibility while maintaining ease of deployment.
Use Cases Where RDS Isn’t a Fit
There are a number of use cases where the inherent limitations of RDS make it not a good fit. With RDS, you are trading off the flexibility to deploy complex environment topologies for the ease of deploying with the push of a button, or a simple API call. RDS eliminates most of the operational overhead of running a database in your environment by abstracting away the physical or virtual hardware and the operating system, networking and replication configuration. This, however, means that you can’t get too fancy with replication, networking or the underlying operating system or hardware.
When Using RDS, Which Engine is Right For Me?
Amazon’s RDS has numerous database engines available, each suited to a specific use case. The three RDS database engines we’ll be discussing briefly here are MySQL, MariaDB and Aurora.
Use MySQL when you have an application tuned for MySQL, you need to use MySQL plug-ins or you wish to maintain compatibility to support external replicas in EC2. MySQL with RDS has support for Memcached, including plug-in support and 5.7 compatible query optimizer improvements. Unfortunately, thread pooling and similar features that are available in Percona Server for MySQL are not currently available in the MySQL engine on RDS.
Use MariaDB when you have an application that requires features available for this engine but not in others. Currently, MariaDB engines in RDS support thread pooling, table elimination, user roles and virtual columns. MySQL or Aurora don’t support these. MariaDB engines in RDS support global transaction IDs (GTIDs), but they are based on the MariaDB implementation. They are not compatible with MySQL GTIDs. This can affect replication or migrations in the future.
Use Aurora when you want a simple-to-setup solution with strong availability guarantees and minimal configuration. This RDS database engine is cloud-native, built with elasticity and the vagaries of running in a distributed infrastructure in mind. While it does limit your configuration and optimization capabilities more than other RDS database engines, it handles a lot of things for you – including ensuring availability. Aurora automatically detects database crashes and restarts without the need for crash recovery or to rebuild the database cache. If the entire instance fails, Aurora automatically fails over to one of up to 15 read replicas.
So If RDS Handles Operations, Why Do I Need Support?
Generally speaking, properly using a database implies four quadrants of tasks. RDS only covers one of these four quadrants: the operational piece. Your existing staff (or another provider such as Percona) must cover each of the remaining quadrants.
The areas where people run into trouble are slow queries, database performance not meeting expectations or other such issues. In these cases they often can contact Amazon’s support line. The AWS Support Engineers are trained and focused on addressing issues specific to the AWS environment, however. They’re not DBAs and do not have the database expertise necessary to fully troubleshoot your database issues in depth. Often, when an RDS user encounters a performance issue, the first instinct is to increase the size of their AWS deployment because it’s a simple solution. A better path would be investigating performance tuning. More hardware is not necessarily the best solution. You often end up spending far more on your monthly cloud hosting bill than necessary by ignoring unoptimized configurations and queries.
As noted above, when using MariaDB or MySQL RDS database engines you can make use of plug-ins and inject additional configuration options that aren’t available in Aurora. This includes the ability to replicate to external instances, such as in an EC2 environment. This provides more configuration flexibility for performance optimization – but does require expertise to make use of it.
Outside support vendors (like Percona) can still help you even when you eliminate the operational elements by lending the expertise to your technical teams and educating them on tuning and optimization strategies.