Not all 1TB drives are 1TB? Say what?

[Diggs]

Today I was cloning (ddrescue) a 4-5 year-old SanDisk 2.5" 1TB SSD to a new Samsung 870 2.5" SSD. It failed! Not enough room on the target drive. So I imaged it using Macrium and when I was restoring the image I find out the 1TB Samsung is 20 GB smaller than the SanDisk(?) which is why it failed! Never seen that before. Always thought 1TB was 1TB. Things that make you go hmmmm......

 

[britechguy]

Ah, the dreaded, "Who's using TB for terabyte versus who's using TB for tebibyte [TiB, strictly] conundrum," at least in all likelihood.

What is tebibyte (TiB)? | Definition from TechTarget

Explore the meaning of tebibyte (TiB), what the measurement is used for and how it compares to a terabyte.

www.techtarget.com

It appears that SanDisk was using Tebibyte (1,099,511,627,776 bytes) and Samsung is using Terabyte (1,000,000,000,000 bytes), or something like that.

 

[Sky-Knight]

As stated above
1 TB != 1 TiB

Two different scales! And when you're mucking with SSDs, some of them use the decimal scale, and others use the binary scale.

Samsung is WONDERFUL in this because the CONSUMER grade drives are decimal... but the PROFESSIONAL / ENTERPRISE drives are BINARY!

 

[britechguy]

Note also that Microsoft uses the binary [TiB, GiB] system in Windows. My 1 TB NVMe SSD shows up as 931 GB [which I wish they'd show as GiB], and even accounting for the space taken up by Windows and the filesystem, it's clearly not 1 TiB in capacity when empty, but 1 terabyte (TB).

 

[Diggs]

My 1 TB NVMe SSD shows up as 931 GB

Yup, the Samsung was 931GB but the SanDisk was 953GB. Pffft!

 

[Larry Sabo]

I suspect the difference is due to space allocated for spares, as the difference between GB and GiB does not explain the difference, according to this calculation.