Mutable Vs Immutable Infrastructure – A Comprehensive Guide to Choose the Best

When selecting servers to run your operations, it’s vital to consider if you prefer a moldable environment or a rigid one. The question of mutable vs immutable infrastructure is one all developers need to consider.

Shifting from mutable to immutable infrastructure is a costly venture that includes server management and maintenance practices and convincing the IT security and development team to forget their previous environment and adopt new principles. As you can imagine, such a shift is heavy on all your operations.

Therefore, before deciding to provision or de-provision infrastructure, it’s best to compare and contrast mutable and immutable infrastructure.

What Is Mutable Infrastructure?

The word ‘mutable’ suggests the ability to change- to mutate into something new. In the DevOps world, the advantage of mutability is crucial when you wish to retain previous data without worrying about obtaining new infrastructure. You can apply patches, upgrade or downgrade, and scale up and down.

Let’s say you created a web server and deployed it on existing mutable infrastructure. The users continue making requests to the server, and after a while, you realize that you need to make changes to your server.

What’s excellent about this change is that you don’t have to move existing data to a new machine. You can apply your changes to the existing version and roll out the upgrade. With proper configuration management, you can perform your upgrade successfully.

However, what happens if your upgrade does not run as smoothly as intended. Most changes and upgrades do not run without glitches? What if you compromise the security of your operations? What happens when you wound up with an unplanned version of the upgrade?

There is a considerable risk in making changes, failing in the process, and ending up with a product you do not understand. You cannot run tests or validate products you have little to no knowledge of. Which means you’ll be waddling in a pool of problems that are impossible to debug.

Pros of Mutable Infrastructure

• Your IT team does not need to build servers from scratch every time a change is required.

• You can roll out updates for individual servers, which makes the update process faster.

• You can ensure that the infrastructure used meets the specific needs of each user.

• You can understand each server on an individual level, which makes it easier to diagnose problems.

Cons of Mutable Infrastructure

• Since each server is unique in configuration, it becomes harder to diagnose and manage each server. This is called configuration drift.
• Indiscrete versioning- The changes you make to the server aren’t documented, which makes tracking hard and diagnosing almost impossible.
• Updates can fail due to several reasons, such as DNS failure or poor network connectivity, which all take time to recognize and fix.
• Debugging is time consuming due to update tracking problems. You could end up with several versions of an update without any insight into the problem.

What Is Immutable Infrastructure?

“Immutable” is the state of being unchangeable. It’s an antonym to mutable, which means that on this end, the infrastructure cannot be modified once deployed. When changes are necessary, you need to deploy afresh, add infrastructure, and decommission old infrastructure.

Let’s go back to the example above and replay it with immutable infrastructure. When it’s time to upgrade your server, you don’t roll out an upgrade. Instead, you create a new server, which creates a distinct new machine.

You then give your new creation several tests until it’s perfect and then transfer the traffic. In so doing, you can avoid rolling out a problematic upgrade and only transfer users once you’re sure of the new server’s functionality. What’s more, you don’t end up with several unusable machines.

Once you have the new server, you can decommission the first server.
In a highly interdependent environment, such as cloud or microservices, you can reduce the configuration drift.

Pros of Immutable Infrastructure

• Discrete versioning- Each server version is independent of the other. You won’t have two versions running at the same time.
• Easier Tracking- Since you create new versions of the server when you need to make changes, you can track each version’s mistake. There is no middle zone.
• It’s easier to test different servers and roll out updates since the configurations in each server are consistent.
• You enjoy predictability since the servers remain the same.
• Great for interdependent environments such as cloud technologies.
• You can roll back deployments since previous versions are unaffected.

Cons of Immutable Infrastructure

• You cannot modify existing servers. In case of problems, servers with the same configuration need a complete overhaul.
• You need to externalize data storage instead of copying it to a local disk.

Which Is Right Is For You?

Ultimately, weighing the pros and cons is the best way to choose between mutable and immutable infrastructure.

Choosing mutable infrastructure often comes with the risk of snowflake servers. These are servers that have a unique configuration, and therefore, require manual administration. If something goes wrong, only one IT person familiar with the server can solve the problem. What happens when that specific IT person isn’t around? Will you suspend all operations?

If you’re making changes to several machines, it takes a lot of time. Also, the cleanup process is hectic. If you’re continually deploying upgrades, a mutable infrastructure might not suit your operations.

Immutable infrastructure supports automatic deployment. This type of infrastructure is primarily built around virtualization. You, therefore, don’t have to worry about provisioning and de-provisioning hardware and software as needed. In the cloud environment, you can document all the processes taken to create a resource.

In the DevOps world, limiting dependencies saves time. You want to create a pipeline that supports automated testing and deployment. This way, you can increase your development pace. Manual validations steal crucial time and prevent you from launching new applications faster. You can also reproduce scenarios and perform disaster recovery automatically with immutable infrastructure.

As more businesses continue to turn to cloud-native environments, you’ll inevitably interact with immutable infrastructure. While this type of infrastructure isn’t attack-proof, it’s best to find a solution that automatically detects problems while helping you leverage the cloud environment.