500GB Extreme Portable SSD missing 80% of its space

USB Flash Drives Extreme Drives
1

I have a 500 GB Extreme Portable SSD. It shows 465 available space on ‘Create and Format Hard Disk Partitions’. But I am only able to copy about 125 GB. What happened to the remaining 340+ GB ???

2

Hi @usha

Have you checked our knowledge base articles?
(Get Support for Your SSDs and Flash Products | Sandisk)

Have you opened a Support Case?
If not, contact SanDisk Technical Support for assistance.
(Contact Support | Sandisk)

3

It is because some space might be taken by hidden partitions or the drive could have errors or bad spots. There could also be limits from the file system or settings. To fix this, you should check the drive for errors and look at how the partitions are set up. If needed, back up your data and reformat the drive.

4

Thank you, Usha, please use Sandisk Dashboard to check disk health.

Please use Cmd > Chkdsk for deep disk health check.

You could use a defrag tool, such as Windows Cmd > defrag, or a 3rd party tool, such as Aomei Partition Assistant > defrag.

If that does not fix it. you could create a new Windows user, local / non-microsoft.

5

There are several proven methods to restore a hard drive to its full capacity:

  1. Update the external hard drive driver – Outdated or corrupted drivers can prevent your computer from recognizing the drive correctly. Updating the driver ensures smooth communication between the system and the hard drive.

  2. Update the drive’s firmware – Firmware controls the drive’s operations, and updates can fix bugs, improve stability, and help restore lost capacity.

  3. Initialize the hard drive – Creating a new partition table can fix misconfigurations or corruption that limit the drive’s usable space. Keep in mind that initializing will erase all data on the drive, so back up anything important first.

  4. Run CHKDSK – This built-in utility scans for bad sectors and file system errors, repairing them to make the full capacity available again.

(If you want to learn related information, this how-to article might be useful: Fixed! (External)Hard Drive Shows Wrong Capacity on Windows )

6

Sure! Your SSD’s total space is fine. The issue is likely a partition setup. In Disk Management, you probably see a ~125 GB partition and a large “Unallocated” space. You need to extend the volume to merge them.

Alternatively, check if it’s formatted as FAT32, which has a 4GB file size limit. Reformat to NTFS or exFAT (if used with Mac), but back up your data first as this will erase the drive.