I replaced a 4TB WD Passport hard drive with a 4TB SanDIsk Extreme Portable SSD. The hard drive had about 2TB free space. The SSD has less than 0.5TB free space.
I discovered the reason: The SSD allocates file space in multiples of 1Mb. Not a problem for very large files – I don’t mind if a 500MB file takes up 501MB of space. Different story if a 1KB file takes up 1MB, or a 1.01MB file takes up 2MB.
I have about 1.5 million files (so far) on the drive, most of which are much smaller than 1MB. The excess allocation accounts for most of the lost 1.5TB of storage.
Can I change the minimum allocation to something a lot smaller than 1MB? Maybe 128KB?
Update: I now understand the issue better. The drive uses the exFAT file system format, which is compatible across Windows, Mac, and other devices. For exFAT drives in the 2 to 4 TB range, the “cluster size” (allocation granularity) is defined to be 1MB.
Reformatting the drive to Windows NTFS would solve the wasted space problem, but the drive would be fully usable only on Windows. I’m only using it on Windows computers, so that’s a good solution for me.