Based on the suggestions, first, I tried rsync – it sort of works, but it’s a 
lot of work to do the integration with cron, etc.; and there’s some subtle 
stuff with scheduling that I ran into (you really need to have some 
randomization in the times when it runs, or you wind up running two rsyncs at 
the same time).

I tried syncthing, also based on suggestions – it works great. Trivial install, 
so far (”apt-get install syncthing”) .  I was hoping I’d be able to stay out of 
GUI-land (i.e. I’d rather do configuration changes with ssh than vnc, and, when 
replicating it to new machines, it’s more controllable if it’s a script, and I 
can use pdsh, for instance), but trying to figure out the somewhat complex xml 
config files – GUI did make it easy, so there we are. Worst comes to worst, 
I’ll fire up the GUI on each one in sequence.

But so far, it seems work fine. I was concerned about resources, but for the 
small number of files I’m working with (dozens, not thousands) the time 
required to do the hashing, etc. is tiny (as in <0.1% CPU)

There is a tricky aspect to syncthing – having to do with the timestamps on the 
files, and whether your computer comes up with the “right time” (RPi do not 
have a battery backed up real time clock, so it has to “get time” from NTP, and 
I’ve not got my in-house NTP server running, yet)

I seriously looked at glusterfs – which looks very cool, and is sort of the 
next level of seamlessness – But it seemed a bit heavyweight for this 
application.  I may still look into it, though – I’ve got some ideas which 
might benefit from that almost “multiported, redundant storage” view.



Jim Lux
SunRISE Project Manager
Jet Propulsion Lab
+1(818)354-2075 (office)
+1(818)395-2714 (cell)


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