Discrepancy in Available Space for EBS Volume Expansion on a Windows Instance (possible bug)
Hello AWS Community,
I'm encountering an issue with one of our EBS volumes. I provisioned a 1.2 TiB st1 EBS volume and upon attaching it to a Windows instance, found that only 1.17 TB is available for disk expansion, even after following all standard optimization procedures.
I've already taken into account the:
- Provisioned size in the AWS console.
- Difference between TB and TiB.
- NTFS filesystem overhead.
- Reserved space for system recovery.
Despite these checks, there remains a discrepancy in the available space for volume expansion. This seems to indicate that we're essentially being billed for around 30 GB of space which we cannot utilize for disk expansion purposes.
Has anyone else encountered a similar situation, or is aware of any related bugs or issues?
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This is normal not just for AWS but even when you buy physical disks. The same occurs here. The disk is measured in bytes. However,
One megabyte is about 1 million bytes (or about 1000 kilobytes).
The size of the EBS volume is exactly x thousands kilo bytes. However 1 MB in reality is 1024 bytes.
If you really wanted to 1.2TB you’d have to provision a volume 1.229. 1.2 x 1024
In AWS you are paying for 1200000000 kilo bytes
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Upon a careful review of the information presented in your post regarding data storage sizes, I would like to highlight a few discrepancies:
I noticed that the value available for disk extension in Windows differs from the allocated size on the AWS EBS volume. These values should match.
It depends if your looking at the binary or decimal representation of a megabyte.
https://en.m.wikipedia.org/wiki/Megabyte
Remember a mega or million or terra is a measurement in zeros. Not 1024’s Disks are usually measured in decimal. However.
A common usage has been to designate one megabyte as 1048576bytes
You are correct. The confusion was caused when allocating EBS volumes larges than 1 TB on Windows Server. When attempting to extend a disk that's larger than 1 TB, Windows displays differing values when toggling between TB and GB units. This behavior has added another layer of confusion regarding the disk size and its corresponding charges.