# EC2 Storage in Plain English: Root Volumes vs File Systems

- URL: https://karandeepsingh.ca/posts/ec2-root-volumes-vs-file-systems/
- Author: Karandeep Singh
- Published: 2026-07-30
- Tags: aws, ec2, storage
- Summary: The EC2 launch wizard's storage step has two very different parts, the root volume and the File systems panel, and beginners mix them up. This explains both in plain words, plus when to reach for each.

When you launch an EC2 instance, most of the wizard is quick, name it, pick an operating system, pick a size. Then you hit **Configure storage**, and suddenly there are two sections that look related but are not: a box at the top for the **root volume**, and a panel at the bottom called **File systems** with options like S3, EFS, and FSx.

New folks almost always mix these two up. So this article slows down on exactly that step and explains, in plain words, what each part is and when you would actually use it. It uses the real screenshots from launching a small `demo-web` instance.

**info:**
This is the storage-focused companion to launching your first EC2 instance. You do not need any prior setup to follow along, just an AWS account and the **Launch instance** button. Everything here fits inside the free tier.

## Setting the scene: the launch, in three quick steps

Before the storage step, the wizard asks for three things. I will move through them fast so the storage part has context.

**Name and operating system.** I named the instance `demo-web` and picked **Ubuntu**. Notice the AMI is marked *Free tier eligible*, and near the bottom it says **Root device type: ebs**, that "ebs" is a hint about the root volume we are about to meet.

![The EC2 launch wizard with the name demo-web entered and Ubuntu Server selected as a free-tier-eligible AMI](https://karandeepsingh.ca/images/posts/ec2-launch-name-ami.png)

**A key pair to log in.** I created a key pair named `test` using the **ED25519** type and `.pem` format. This is the private key you use to SSH into the box, download it and keep it safe, because AWS will not show it to you again.

![The EC2 create key pair dialog with an ED25519 key named test and the .pem format selected](https://karandeepsingh.ca/images/posts/ec2-create-key-pair.png)

**Network and firewall.** The wizard made a security group called `launch-wizard-1` and, by default, opened **SSH from Anywhere (`0.0.0.0/0`)**. AWS even shows a yellow warning about it, and it is right to. For anything real, you would change that SSH source to **My IP** so the whole internet cannot knock on your door. For a five-minute demo it is fine, but notice the warning is there for a reason.

![EC2 network settings showing the launch-wizard-1 security group with SSH open to anywhere and a warning](https://karandeepsingh.ca/images/posts/ec2-network-security-group.png)

Now the part we came for.

## Part 1: the root volume, your instance's own disk

The top box in **Configure storage** is your **root volume**. Think of it as the built-in hard drive of your server. It is where the operating system from the AMI lives, plus anything you install later. In my case: **8 GiB**, type **gp3**, labeled **Root volume, 3000 IOPS, Not encrypted**.

![EC2 configure storage step showing an 8 GiB gp3 root volume and the File systems panel set to None](https://karandeepsingh.ca/images/posts/ec2-storage-root-volume-file-systems.png)

A few plain-English facts about the root volume:

- **It belongs to one instance.** Just like the C: drive on a laptop, no other server shares it. If you launched five instances, each gets its own separate root volume.
- **It is an EBS volume.** EBS (Elastic Block Store) is AWS's disk-in-the-cloud service. The disk is not physically inside the server, it is attached over the network, but to the operating system it looks and behaves like a normal local drive.
- **By default it disappears with the instance.** The root volume is set to *delete on termination*. Terminate the instance and the disk (and everything on it) is gone. That is usually what you want for a throwaway box, but it is the single biggest "where did my data go" surprise for beginners.
- **It lives in one Availability Zone.** An EBS volume is tied to the same AZ as its instance. You cannot attach it to an instance in another zone.

**tip:**
Rule of thumb: put the operating system and your app on the root volume, but do not keep anything you truly care about *only* there. Important data belongs somewhere that outlives a single instance, a separate EBS data volume you back up, or one of the file systems below.

### Root volume types (the gp3 dropdown)

Open the type dropdown and AWS offers several disk types. Here is the same list, in plain terms:

![The EC2 root volume type dropdown listing gp3, gp2, io1, io2, sc1, st1 and Magnetic options](https://karandeepsingh.ca/images/posts/ec2-storage-volume-types.png)

| Type | What it is | Reach for it when |
|---|---|---|
| **gp3** (General Purpose SSD) | The modern default. Fast SSD, steady 3000 IOPS baseline, best price for performance | Almost everything, this is the right default |
| **gp2** (General Purpose SSD) | The older general-purpose SSD; speed scales with size | Only if you have a specific reason; gp3 is usually better and cheaper |
| **io1 / io2** (Provisioned IOPS SSD) | You pay for a guaranteed, very high number of IOPS | Demanding databases that need consistent, heavy disk performance |
| **sc1** (Cold HDD) | Cheap spinning-disk storage for data you rarely touch | Big, infrequently accessed data, *not* a root volume |
| **st1** (Throughput Optimized HDD) | Cheap disk tuned for large sequential reads | Big streaming workloads like logs or data processing, *not* a root volume |
| **Magnetic** (standard) | Previous-generation magnetic storage | Legacy only; avoid for new work |

Notice that **sc1** and **st1** are greyed out in the screenshot with "not compatible with root volumes." That is the wizard reminding you those HDD types are meant for extra *data* volumes, not for booting an operating system. For the root disk, **gp3 is the answer 95% of the time.**

## Part 2: the File systems panel, shared storage that lives on its own

Below the root volume is a panel titled **File systems**, with four choices: **S3 Files - new**, **EFS**, **FSx**, and **None** (selected by default).

This is where the confusion starts, so here is the key idea:

> A **root volume** is one instance's private disk. A **file system** is separate, shared storage that many instances can connect to, and that keeps existing even after every instance is gone.

You do not need a file system to run a server, that is why **None** is the default. You add one when several machines need to share the same files, or when you need storage that outlives any single instance. Here is what each option means.

### EFS, a shared folder for many Linux servers

**Amazon EFS** (Elastic File System) is a managed shared file system for Linux. Many instances, even across different Availability Zones, can *mount* it at the same time and all see the same files instantly. It grows and shrinks automatically, you never pick a size.

**Use it when:** several servers need to read and write the same files, a fleet of web servers serving the same uploads, a shared home directory, a content folder behind a load balancer.

### FSx, managed file systems for Windows and high performance

**Amazon FSx** is a family of managed file systems for more specialized needs. The common ones are **FSx for Windows File Server** (a proper Windows/SMB network share) and **FSx for Lustre** (an ultra-fast file system for heavy compute like machine learning or simulations).

**Use it when:** you need a Windows file share with Active Directory, or seriously high-performance shared storage for HPC-style workloads.

### S3, cheap and massive object storage

**Amazon S3** is object storage, the internet's default bucket for files. It is not a normal disk, but AWS now lets you *mount* an S3 bucket so it looks like a folder on your instance. It is extremely cheap, essentially unlimited, and reachable from anywhere, but slower and less "filesystem-like" than EFS.

**Use it when:** you are storing lots of files that do not need low-latency disk behavior, backups, images and videos, logs, data-lake files, static website assets.

### None, the honest default

For a single server, **None** is correct. Your instance runs entirely on its root volume, and there is nothing extra to configure, pay for, or clean up. Only add a file system when you actually have the "many machines share this" or "must outlive the instance" problem.

## Root volume vs file system: the one-glance mental model

| Aspect | Root volume (EBS) | File system (EFS / FSx / S3) |
|---|---|---|
| **Who can use it** | One instance only | Many instances at once |
| **What it feels like** | The C:/ drive on a laptop | A shared network drive |
| **Survives instance deletion?** | No, deleted by default | Yes, it lives on its own |
| **Where it lives** | One Availability Zone | Across zones / regions (varies) |
| **You need it to boot?** | Yes, the OS lives here | No, it is optional extra storage |
| **Good for** | The OS and the app itself | Shared files, backups, big data |

## When do you actually use each? A quick decision guide

- **Running one simple server or app?** The **root volume** alone is enough. Maybe bump it from 8 GiB if you need room.
- **Need more disk on one box, separate from the OS?** Add a second **EBS data volume** (gp3). It can survive even if you rebuild the instance.
- **Several Linux servers sharing the same files?** Reach for **EFS**.
- **Windows file share, or HPC-grade shared storage?** That is **FSx**.
- **Piles of backups, media, logs, or data-lake files?** Use **S3**.

## What it costs (and staying free)

The root volume in this demo, 8 GiB of gp3, is comfortably inside the free tier (up to 30 GB of EBS is free for the first year). EFS, FSx, and S3 all bill separately, which is another reason to leave **File systems** on **None** until you genuinely need one. And remember: because the root volume deletes on termination, tearing down the demo instance also removes its disk, so there is nothing lingering to pay for.

## Wrapping up

The storage step trips people up only because two unrelated things sit next to each other. Once you see it clearly, it is simple: the **root volume** is your instance's private boot disk (use **gp3**), and the **File systems** panel is optional shared storage you bolt on when many machines, or long-lived data, need it. Most first instances want a gp3 root volume and nothing else.

If you are scripting any of this against AWS afterwards, my [Python Boto3 cheatsheet](https://karandeepsingh.ca/cheatsheets/python/python-boto3/) and [Ubuntu Terminal cheatsheet](https://karandeepsingh.ca/cheatsheets/terminal/ubuntu-terminal/) pair nicely with a fresh EC2 box.

## References and Further Reading

- Amazon Web Services. [Amazon EBS volume types](https://docs.aws.amazon.com/ebs/latest/userguide/ebs-volume-types.html).
- Amazon Web Services. [Amazon EFS User Guide](https://docs.aws.amazon.com/efs/latest/ug/whatisefs.html).
- Amazon Web Services. [Amazon FSx](https://docs.aws.amazon.com/fsx/).
- Amazon Web Services. [Mountpoint for Amazon S3](https://docs.aws.amazon.com/AmazonS3/latest/userguide/mountpoint.html).

**Question:** For your own workloads, where do you draw the line between a bigger EBS data volume and moving to a shared file system like EFS?

## Quiz

1. What is the "root volume" when you launch an EC2 instance?
   a) A shared network drive that many instances read from at once
   b) The instance's own disk, where the operating system lives
   c) A backup copy of your instance stored in S3
   d) The physical hard drive inside the AWS data center
   Answer: b. The root volume is the boot disk attached to that one instance. It holds the operating system from the AMI plus whatever you install. It is private to the instance, like the C drive on a laptop.

2. You have five web servers that all need to read and write the same folder of uploaded files. Which storage fits best?
   a) A bigger root volume on each server
   b) Amazon EFS, one shared file system all five mount
   c) A separate S3 bucket per server
   d) Provisioned IOPS (io2) root volumes
   Answer: b. A root volume belongs to a single instance, so five servers would each have their own separate copy. EFS is a shared file system that many instances mount at the same time, so all five see the same files instantly.