Why can’t I expand my volume past 2 TB on an Amazon EC2 Windows instance?

Resolution

Amazon EBS, with a Master Boot Record (MBR) partition, allows a maximum disk storage capacity of 2TB. This is the Microsoft's hard limit for MBR and can't be extended. If your Windows Amazon Machine Images (AMI) uses MBR, your boot volume has a limit of 2047 GB.

However, your non-boot volume doesn't have this limit. Windows' non-boot volumes that are 2 TB (2048 GB) or larger must use a GUID partition table (GPT) to access the entire volume. When you attach an EBS volume over 2 TB to a Windows instance at launch, it automatically formats the GPT partition table. If you attach the EBS volume over 2 TB to a Windows instance after launch, you must manually initialize it with a GPT table.
Note: Use the Microsoft tool MBR2GPT.exe to extend the boot volume to more than 2TB on an MBR partition. MBR2GPT converts the disk from MBR to the GPT partition style without modifying or deleting the disk data.

Extend the non-boot volume size to over 2TB

Note: As a best practice, before you begin, create a snapshot of the volume to save any valuable data. Then you can use the snapshot to roll back your changes as needed. For more information, see Create Amazon EBS snapshots.

Follow these steps to extend the non-boot volume:

1. Log in to your Amazon EC2 console.
2. Choose Volume.
3. Create a new, empty volume in the same Availability Zone as the instance. Then, attach the volume to your EC2 Windows instance.
4. Use Remote Desktop Protocol (RDP) to connect to your EC2 Windows instance.
5. Open a command prompt. Then, run the diskmgmt.msc command to launch Disk Management. From Action, choose Refresh.
6. In Disk Management, select and hold (or right-click) the disk that you want to initialize, and then choose Initialize Disk. If the disk is listed as Offline, first select and hold (or right-click) the disk, and then choose Online.
7. In the Initialize Disk dialog box, make sure that you selected the correct disk. Then, choose GPT as partition style.
8. Select and hold (or right-click) the unallocated space on the drive. Then, choose New Simple Volume.
9. Choose Next. Specify the size of the volume, and then choose Next again. For volume, keep the default size, which uses the whole drive.
10. Specify the drive letter that you want to assign to the volume, and then chose Next.
11. Specify the file system that you want to use (usually NTFS). Choose Next, and then choose Finish.
12. Copy the data from the original volume to the new volume using a tool such as Microsoft's Robocopy.
13. In Disk Management, take the old volume Offline, and assign the old volume drive letter to the new volume.
14. In the Amazon EC2 console, detach the old volume from the instance.
15. Reboot the instance to verify that it functions properly. Then, delete the old volume.