Merlin Mann: "Unison is my synching tool of choice"

I wonder how this compares with ChronoSync

I like that it's free! I've been using an Automator script to synch my Address Book and iCal across three Macs (since I don't have .Mac), but this looks much simpler. Funny you should post this, as I was just looking at ChronoSync the other day.

(Sorry for not answering earlier, I was traveling with no internet access.)

The differences with ChronoSync are difficult to point out as many technical details are different. The way Unison works is that it detects changes on files by states: it remembers the contents of the file at last synchronization (using a hash) and it may thus know which file has changed without relying on the modification date.

ChronoSync looks prettier, and one advantage it may have is in the amount of HFS+ metadata it's able to synchronize. Unison can synchronize resource forks, for instance, but it does not synchronize extended attributes (which ChronoSync seems to be able to sync).

On the other hand, Unison is multi-platform (one may synchronize an OS X machine with a Linux or Windows machine), has a well defined semantics, is fast (it implements rsync for network transfers and has many tricks to speed up file change detection), and it's free. It can also see when a file has moved so that there is no need to transfer it again.

I'm using Unison to keep my 3 macs in sync (synchronizing basically the whole home directory), as well as to do automated backups and publish some web pages. I'd highly recommend you give it a try ;-)

Great information - thank you for the tip. I'm going to download it now. I'm more than ready to ditch my kludgy Automator solution, and this looks to be exactly what I need.

I'd love to use unison but it seems unable to handle extended characters. I'm trying to use it to keep a few hundred thousand mp3s in sync across machines, but keeping umlats and accents out of the filenames is probably impossible.

Rex Roof: the handling of extended characters seems to depend on the architecture you're on. I'm synchronizing OS X to OS X and everything works fine. In an heterogeneous setting, things fail however (as Unison does not translate between the different encodings).

So I use many accented characters, but do not do heterogeneous synch.