journalaws / ec2 / storage

*Attaching and Expanding an EBS Volume on a Windows EC2 Instance

May 19, 2026·8 min read
Architecture diagram for Attaching and Expanding an EBS Volume on a Windows EC2 Instance

Summary

In this lab I launched a Windows EC2 instance and connected to it over Remote Desktop. I then created a separate EBS volume for extra storage, attached it to the instance, and initialized it in Windows Disk Management so it appeared as a new drive. Finally, I increased the volume's size in AWS and extended the drive in Windows to use the extra space.

Lab Environment

SettingValue
RegionCanada (Central) ca-central-1
Instance nameWindowsInstance
AMIMicrosoft Windows Server 2019 Base (Free tier eligible)
Instance typet3.micro (2 vCPU, 1 GiB memory)
Key pairdemo (RSA, .pem)
NetworkDefault VPC, subnet in ca-central-1a
Security groupNew security group (RDP, TCP 3389)
Root volume30 GiB gp2 (C: drive)
Additional volumegp3, 15 GiB, later increased to 30 GiB (D: drive)

Part 1: Launching the Instance

1. Opened EC2 and named the instance

I searched for EC2 in the AWS Console, opened Instances, and clicked Launch instances. Under Name and tags, I named the instance WindowsInstance.

2. Chose the AMI and instance type

Under Application and OS Images, I clicked Browse more AMIs and selected Microsoft Windows Server 2019 Base, after confirming it was Free tier eligible. For the instance type, I chose t3.micro, which gave me 2 virtual CPUs and 1 GiB of RAM.

3. Created a key pair

I clicked Create new key pair, named it demo, chose RSA and .pem, and clicked Create key pair. The private key downloaded automatically, and I saved it for retrieving the Windows password later.

4. Configured network settings

I clicked Edit under Network settings, kept the default VPC, and selected the subnet in ca-central-1a. Choosing the subnet myself was important for this lab, because the EBS volume I created later had to be in the same Availability Zone as the instance.

I chose Create security group and kept the default RDP rule (TCP port 3389) that AWS adds for Windows instances.

5. Configured storage

I kept the default 30 GiB gp2 root volume, which is where Windows is installed. The Add new volume button on this page could have added a second volume at launch, but I left it alone because I wanted to create and attach one separately after launch.

6. Launched the instance

I clicked Launch instance and waited for the status check to change from Initializing to 3/3 checks passed.

Part 2: Connecting to the Instance

  1. I selected WindowsInstance, clicked Connect, opened the RDP client tab, and clicked Download remote desktop file.
  2. I clicked Get password, uploaded demo.pem with Upload private key file, and clicked Decrypt password.
  3. I opened the downloaded RDP file, clicked Continue on the trust prompt, pasted the decrypted password, and clicked Connect.

The Windows Server desktop loaded.

Part 3: Checking the Existing Storage

Inside the instance, I pressed Windows + R, typed diskmgmt.msc, and clicked OK to open Disk Management.

There was only one disk: Disk 0, 30 GB, holding the C: drive. This is the root volume, and it holds the operating system. In practice, application data and files are usually kept on a separate volume rather than on the root drive, so I decided to add another one.

Part 4: Creating and Attaching a New EBS Volume

1. Opened the Volumes page

Back in the EC2 console in my browser, I went to Elastic Block Store → Volumes in the left menu. The only volume listed was the instance's 30 GiB gp2 root volume.

2. Created the volume

I clicked Create volume and used these settings:

SettingValue
Volume typeGeneral Purpose SSD (gp3)
Size15 GiB
IOPS3000 (default)
Throughput125 MiB/s (default)
Availability Zoneca-central-1a
SnapshotDon't create volume from a snapshot
EncryptionNot encrypted

The Availability Zone was the most important setting. An EBS volume can only attach to an instance in the same AZ, so I matched it to the instance's AZ, ca-central-1a. I clicked Create volume, and the new 15 GiB gp3 volume appeared in the list next to the root volume.

3. Attached the volume

I selected the new volume and clicked Actions → Attach volume. For Instance, I chose WindowsInstance. The list only showed instances in the same AZ as the volume. For Device name, I chose xvdf, which AWS recommends for Windows data volumes. Then I clicked Attach volume.

Part 5: Setting Up the Drive in Windows

1. Found the new disk

Back in Disk Management on the instance, a new disk appeared: Disk 1, 15 GB, marked Unknown and Not Initialized, with all its space Unallocated. It didn't show up in This PC yet, because Windows can't use a disk until it's initialized and partitioned.

2. Initialized the disk

I right-clicked Disk 1 and selected Initialize Disk. In the dialog, I left Disk 1 checked, kept the partition style as MBR (Master Boot Record), and clicked OK. The disk changed to Basic and Online.

3. Created a new volume

I right-clicked the unallocated space on Disk 1 and selected New Simple Volume. I clicked Next through the wizard, keeping the default size, drive letter, and NTFS formatting, and clicked Finish.

4. Confirmed the new drive

I opened This PC. A new drive, New Volume (D:), appeared next to C:, showing 14.9 GB free of 14.9 GB.

Part 6: Increasing the Volume Size

Next, I simulated running out of space on the D: drive and needing more storage.

1. Modified the volume in AWS

In the EC2 console, on the Volumes page, I selected the 15 GiB gp3 volume and clicked Actions → Modify volume. I changed Size from 15 to 30 GiB, left IOPS and throughput unchanged, and clicked Modify. The volume stayed attached and in use the whole time.

2. Checked the drive in Windows

When I opened This PC again, D: still showed 14.9 GB. Increasing the volume in AWS added space to the disk, but Windows doesn't automatically grow the existing partition into it.

3. Extended the volume in Windows

I opened Disk Management again with Windows + R → diskmgmt.msc. Disk 1 now showed 30 GB total: the original 15 GB D: partition, followed by 15 GB Unallocated.

I right-clicked New Volume (D:), selected Extend Volume, clicked Next through the wizard to add all the unallocated space, and clicked Finish.

4. Confirmed the new size

I closed Disk Management and opened This PC. The D: drive now showed 29.9 GB free of 29.9 GB. The volume had grown without being detached or reformatted.

What I Learned

  • EBS (Elastic Block Store) volumes are network-attached virtual disks for EC2 instances. Every instance has a root volume, and more volumes can be attached for extra storage.
  • An EBS volume and the instance it attaches to must be in the same Availability Zone.
  • Attaching a volume in AWS isn't enough on its own. Windows needs it to be initialized, partitioned, and formatted before it shows up as a drive.
  • Volume sizes can be increased while the volume is in use, without detaching it or stopping the instance.
  • After increasing a volume in AWS, the operating system also has to extend the partition to use the new space.
  • Windows shows 15 GiB as about 14.9 GB because of file system overhead and the difference between how AWS and Windows report sizes.
  • gp3 volumes include 3000 IOPS and 125 MiB/s of throughput by default, regardless of size. With gp2, performance increases with volume size.

Notes

  • EBS volumes can be made larger, but never smaller. To shrink storage, I would have to create a new, smaller volume and copy the data over.
  • After modifying a volume, AWS requires waiting at least six hours before modifying it again.
  • A volume attached after launch isn't deleted automatically when the instance is terminated, unlike the root volume.

Cleanup

After finishing the lab, I deleted everything I created so it wouldn't keep incurring charges. EBS volumes are billed for their full size whether or not they're in use, and a running instance is billed by the hour along with its public IPv4 address.

1. Detached and deleted the extra volume

  1. Inside the instance, I opened Disk Management, right-clicked Disk 1, and selected Offline so Windows stopped using it.
  2. In the EC2 console, I went to Elastic Block Store → Volumes, selected the 30 GiB gp3 volume, and clicked Actions → Detach volume.
  3. I waited for its state to change from In-use to Available, then clicked Actions → Delete volume and confirmed.

2. Terminated the instance

I went to Instances, selected WindowsInstance, and clicked Instance state → Terminate (delete) instance. Terminating it also deleted its 30 GiB gp2 root volume, because root volumes are set to delete on termination by default.

3. Deleted the security group

Once the instance showed Terminated, I went to Network & Security → Security Groups, selected the security group created for this lab, and clicked Actions → Delete security groups. A security group can't be deleted while an instance is still using it, so this had to wait until after termination.

4. Deleted the key pair

I went to Network & Security → Key Pairs, selected demo, and clicked Actions → Delete. I also deleted the demo.pem file from my computer, since it no longer matched any instance.

5. Confirmed nothing was left

I checked that the Volumes page didn't list any volumes from this lab and that the Instances page showed only the terminated instance. Terminated instances disappear from the list on their own after about an hour and aren't billed.