Hi there!
I thought about first posting here before opening an issue for the project.
So I am using Systemd’s Homed functionality.
It basically stores the user’s home directory as a disk image and it is mounted as a loopback device on authentication.
This is a very nice technology as it provides further security, portability and out of the box options for FIDO2 authentication for instance. However as it is not shipped by default, most Linux users do not even know it exists.
It actually plays together well with Kopia, all I have to back up are the image files for the user. A version of this backed up file fully describes the user.
However, there is 1 problem: when Kopia reads this file, it actually causes hard stuttering for anything which reads or writes to this looped back files when the user is logged in or tries to log in.
As I automate my backups, I have not really found a sensible solution to “dodge” the user being logged in. So rather then trying to find a workaround, I would like to get to the bottom of this.
I am using btrfs as a backing storage for the images (the partition itself the images are stored on are encrypted as well) and the images are use btrfs as well, encrypted via LUKS.
Is this problem caused by Kopia being too “agressive” and causing deadlocks? Or is this a combination of everything I use? I would like to point out that this only occours when backing up these homed images, otherwise not.
I am not really sure, so if anybody has ideas and are willing to uncover and help fix it I am happy to work together just reply to the post to get started or if you are simply curious or maybe are in the same/similar situation.