moved files to another FS and now borg takes a A LOT of time

[shamefulCake1]

I moved my file storage to another FS (LVM+ext4->btrfs), and now borg takes a A LOT of time to process it. The data didn't change, while copying I used 'rsync -a', mtime didn't change. What is it that borg is looking at to find out that files need to be re-hashed?

If it is looking at some unknown metadata, is it possible to work around this?

[ThomasWaldmann]

borg maintains a "files cache" where it remembers H(path) -> (size, ctime, inode) (defaults, see --files-cache option).

In your case, guess inode and ctime changed, so it considers the file as potentially modified and rehashes it.

It is only for the first backup - after that, everything is fast as usual (because it has remembered the new metadata).