Peter's Blog

I've been plying with unison recently, as a means of replicating my collection of 3000 photos between two computers: I nearly lost all the family photos once before, and I have been neglecting backups. With my new strategy of having the dell D410 fire up in it's docking station every night and doing backups, it can also synchronise the photo collection with the 500m which runs all the time.

The advantage of unison over rsync is that it synchronises a pair of directories, i.e. if you add, edit or delete files on one copy then the other copy will be updated accordingly. This is a bi-directional thing, changes made to the second copy will be replicated in the first. In the case of my photo's, I always use the 500m to copy them from the camera but I am likely to use the D410 to manipulate them and what I want is changes in one archive to be fed into the other.

The invocation of unison that I have come up with so far is:

unison -batch -fastcheck true <path1> <path2>

-batch

tells unison not to ask me stupid questions, it will reconcile problems automatically where it can. -force can be used toi resolve conflicts in favour of one of the paths.

-fastcheck true

tells it to compare files by timestamp and length rather than a full binary compare, as is the default under windows.

I have been using a native windows build of unison rather than the cygwin version, mainly because the windows version handles windows file names transparently, including network file names. cygwin unison via ssh does not seem to be able to find any of the file paths I give it (e.g. /cygdrive/c/blah, the cygwin form of c:\blah) and doesn't like network path names (e.g. \\server\share).

Still, it is not working properly for my photo collection but it may be because the network is not reliable enough to handle 3000 photos and 3G worth of data with absolutely no network problems. This may be another sign that the Wifi on the 500m is iffy (iffy wifi ha!) as the d410 in it's docking station has wired networking available.

Have I mentioned recently that the d410 is really nice? The 500m screen seems huge when I go back to it but the d410 is so fast, small and light.