Speed Up Restic Backups After a Drive Replacement

I recently had to upgrade an external hard drive to a higher capacity. I used rsync in the archive mode to ensure I preserved all the necessary metadata. One of the main reasons for this was to avoid having to re-read the whole drive in backup programs (due to changed timestamp). In the case of restic though it was scanning all the files nonetheless.

After some digging, I figured out the issue. Restic along with a metadata changes also checks whether the inode of the file has changed. While rsync can preserve many things, inodes is not one of them because they are automatically assigned. This means the files on the new drive have been identical to the original in all but their inodes. Fortunately restic has an option to skip the inode check which is aptly named --ignore-inode. Using that argument restic was flying though the already backed up files in no time.