archive and synchronizations with unison and rsync


Vinh Nguyen


July 22, 2011

I use rsync as my primary backup utility as it is fairly efficient at archiving files (NOTE: to backup to fat32 usb drives, make sure --modify-window=1 is used). I recently discovered unison, and am using it for real time synchronization between directories from two Linux computers. I really like it.

Because of how well unison works for syncing my two computers in real time, I wanted to compare it to rsync for backing up files (one-way) to different computers and to usb drives (use the -force /first/location for one way syncs). This post does a good job describing unison's capabilities. I tried unison in batch mode to sync between two Linux computers, and it too was quite fast (even faster than rsync).

However, it is horrendously slow when transferring to a FAT drive since it uses checksum on all the files; it is discussed in the comments here.

For my current backup needs, I can use rsync or unison for backups between Linux computers or ext formatted drives; I will probably rely more on rsync since unison isn't installed by default on all Linux machines and the same version is required on the linked machines. For archiving to a FAT32 usb drive, I will rely on rsync. For real-time synchronizations, I will rely on unison.