Filesystems are weird

While cleaning up some files I encountered a curious conundrum.

Every now and then I try to tidy some of the entrophy in my life, as in tidying up the amount physical and digital stuff I’ve accumulated.

So, here’s the curious thing.

I have a folder with various projects I’ve accumulated over the years. Right-clicking on it and inspecting it on my laptop reveals: 259 139 items, amounting to 30.5GB. The filesystem type is ext4.

To speed up the backup process, I combined all the files into a .tar file. The file size of the .tar file ended up being 30.5GB, which makes sense since I didn’t use compression. Transferring the .tar file over the local network took approximately 4 min, while my first attempt at just transferring all the file estimated to take 4 hours.

The weird thing is that after transferring the file to my NAS (Network Accessible Storage), I noticed that the .tar file’s size was 28.36GB. Uh oh! Did everything actually transfer then? There had been no errors during the transfer.

After unpacking the .tar file on my NAS, I inspected them through the NAS’s Web UI, which showed this info about the unpacked folder: 28.19GB, 194 978 files and 66732 folders, which totalled 261 710 items. The file system on my NAS is Btrfs.

Weird. 😤 Both file size and number of items seem to be fluctuating. Even though I saw no errors, I still felt uneasy, considering this is supposed to be backing things up properly.

After a bit I went back and checked the files, by connecting to my NAS from my PC using the SMB protocol (like visiting a shared folder on the network). Inspecting the same files revealed yet other numbers: 30.5GB was the size of the newly transferred .tar file. And inspecting the unpacked folder showed 263 038 items, and total file size 30.3GB.

Some source online point to differences between file systems, which can lead to the same files taking up different amount space. Though, it’s a bit puzzling that the number of files would change as well.

I guess I just need to trust that nothing has been lost in the transfer. The numbers are almost aligned. Hopefully, I won’t end up in a situation where I’m almost able to recover my files.