I've set up a second server with 2*2TB drives in xfs format, I've disabled docker and VM and deleted the dcoker and libvirt images, but I'm still seeing 14GB used on both discs which are currently in the array (no parity for now).

 

I understand xfs has an overhead of 1GB for TB but 14GB seems excessive.

 

On browsing the drives, all I can see are the 4 folders it creates, but nothing inside them, where is the space being used?

XFS added some file system features recently which likely account for the space.

 

Think of the file system like the physical filing cabinets that hold folders and pieces of paper. The drawers and folders all need labels to help you find the specific piece of paper you are after. By keeping the content organization scheme robust and complete, it's quicker to access the needed content, and should some papers get scrambled or misplaced, it's easier to recover if the drawers and folders have more information about what should be where.

 

By reserving the majority of space that could be needed ahead of time, you can ensure a lot of the meta-data is in the quicker portions at the beginning of the drive and doesn't get fragmented across the platters.

Are the drives encrypted?  Probably not or I feel you would have mentioned that.  But I was surprised that encryption used up about 21GB of a 3TB drive.

36 minutes ago, Energen said:

Are the drives encrypted?  Probably not or I feel you would have mentioned that.  But I was surprised that encryption used up about 21GB of a 3TB drive.

No they're not encrypted, it does seem excessve to lose 14GB of each drive though!

5 minutes ago, Spies said:

it does seem excessve to lose 14GB of each drive though!

It is, but like mentioned it's what a recent xfs fs requires, mostly for reflink support.

Does unraid actually use reflink in any way?

Not directly, but anyone can use it if advantageous, I use a lot of reflinking on my btrfs pools.