I just installed the PiDrive to my RPI, and followed to instructions to create an ext4 drive. It says my current size is 870gb/916.7gb. Is this normal? It is using almost 50gb already without me even putting anything in there?
A formatted hard drive capacity is always less, maybe changing filesystem would help.
I was able to get 931.58 GiB out of my 1TB WD harddrive - do harddrive always have (so much) less capacity than the label says (1TB)? It is formatted to NTFS.
Hey there, @Jonas_Techen! 
This is something that you can encounter with any hard drive, really. In order to be simple and consistent, Western Digital and any other HDD manufacturer markets drives in terms of decimal capacity. This basically means that 1 TB equals 1,000,000,000,000 bytes
However, this is not how the file system sees the drive. Operating systems usually use the binary (base 2) numbering system. So, the file system assumes 1 TB equals 1,099,511,627,776 bytes.
Both numbering systems translate to the same amount of storage capacity - meaning there is no storage lost, it’s just how the information is represented. This is similar to the difference between 0 degrees Celsius and 32 degrees Fahrenheit. It is the same temperature, but will be reported differently depending on the scale you are using.
You can read a more detailed article about the Decimal vs. Binary difference and how HDD capacity is indicated in our knowledge base.
Hope this was helpful. Let me know if you have more questions! 
SuperSoph_WD
