Intermediate 15 min read

EBS: Elastic Block Store

By the end of this lesson, you'll be able to:

Distinguish EC2 (compute) from EBS (block storage) as two separate but related services
Explain what a root volume is and what it means for data to persist across a stop/start cycle
Describe, at a beginner level, what an EBS snapshot is for

Prerequisites: "Security Groups and Elastic IPs"

Two different services, working together

It's easy to think of "the EC2 instance" as one single thing, but compute and storage are actually two separate AWS services working together: EC2 provides the virtual server itself — the CPU and memory that run your operating system and software — while Amazon EBS (Elastic Block Store) provides the persistent disk storage that instance's operating system and data actually live on.

Every EC2 instance running a standard AMI has at least one EBS volume attached: its root volume, holding the operating system itself. Additional EBS volumes can be attached for extra storage, separate from the root volume.

Persistence: what survives a stop, what doesn't

An EBS volume's data persists independently of the instance's running state — stopping an instance doesn't erase its root volume's contents; starting it again resumes with that data intact. This is worth stating precisely because it matters for the next lesson's central distinction: while EBS data survives a stop, it does not necessarily survive a terminate, depending on how the volume is configured — another reason "stop" and "terminate" are not interchangeable ideas.

Snapshots: a point-in-time backup

An EBS snapshot is a point-in-time backup of a volume's contents, stored separately from the volume itself. At a beginner level, the concept to take away is simple: a snapshot lets you capture a volume's state and restore a new volume from it later, which matters both for backup purposes and for creating custom AMIs from a configured instance's storage.

Storage isn't free to leave lying around

Just like an Elastic IP, an EBS volume can have cost implications on its own, independent of whether an instance is currently running — an unattached volume left behind after an instance is gone doesn't disappear by itself, and shouldn't be assumed harmless just because nothing is actively using it. Deleting storage you no longer need is a deliberate step, covered again in this module's closing cleanup lesson.

Exercise

Explain, in your own words, the difference between EC2 and EBS — as if explaining it to someone who keeps saying "the EC2 instance's hard drive" and treating EC2 as if it includes storage as part of the same service.

Show hint

One is compute, the other is where that compute's data actually lives — and it has its own lifecycle.

EBS: Elastic Block Store Quiz

1. Which statement correctly distinguishes EC2 from EBS?

EC2 provides the compute (virtual server); EBS provides the persistent block storage it uses EC2 and EBS are two names for the exact same service EBS provides compute, and EC2 provides storage EBS only exists for instances that have never been stopped

2. An EBS volume left over after its instance is gone will automatically be deleted at no cost.

True False

My Notes

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Summary

Amazon EBS provides the persistent block storage volumes an EC2 instance's operating system and data actually live on — a separate service from EC2 itself, with its own lifecycle, its own snapshot mechanism for point-in-time backups, and its own cleanup responsibility when no longer needed.

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