Tuesday, March 11, 2008

Playing with Time-Machine

The latest version of Mac Os comes with automated backup system called time machine, which besides the cool GUI is basically taking periodic snapshots of all changes and saves them to an attached disk. Since my new 17' Powerbook is suspended most of the time and moving back and forth between home and office, any solution which assumes a static environment is going to be challenging.

I was hoping for a solution which would automatically back up any changes incrementally to my linux server at home, whenever the laptop finds itself on that network. This means, the system would have to auto discover its network environment and deal with interruptions, since I am not going to wait for any invisible backup job to complete before closing the laptop again.

Following these instructions , I created an AFP share from my linux server, including a bonjour zero-conf advertisement, which can easily be discovered in the network neighborhood and mounted as a share on the mac. Despite Apple's stated commitment for zero-conf plug-and-play wireless networking, there does not seem to be a way for a share to be automatically re-mounted whenever it becomes in reach. Funny enough, this seems to work only for AFP shares exported from Apple's own new Airport extreme base-stations, which can double as a network share based on an USB attached or built-in hard-disk. Unfortunately, nobody seems to have reverse engineered yet how that is done to replicate it on linux... Another interesting quirk by Apple is that Time-Machine does not work with any AFP shares other than those base-stations anyway - something which can be circumvented pretty easily.

So far, I can at least activate time machine on that network share to play with it, but given that it will time out when disconnected and not re-connect when back in range takes out most of the fun. In addition, Time-Machine seems to want to complete writing one of its snapshots and doesn't' re-try incrementally, which means it may never finish a single one if my laptop never stays online long enough. In addition, Time-Machine seems to have a tendency to fill out any available disk-space which is quite nasty on any shared disk unless it is given a dedicated disk.

All in all, I don't seem to be able to get Time-machine to do what I want - except maybe by spending another $300 for Apple's new Time-Capsule base-station with file-server, which might get closer to a usable solutions for mobile host like my laptop. On the other hand Time-Machine seems very rigid and not very thought out yet, but I like the basic concept so maybe it is time to build something myself...