Re: [Nmh-workers] sync'ing an mh mailstore between two machines?

[bergman]

In the message dated: Wed, 21 May 2008 15:27:03 EDT,
The pithy ruminations from Paul Fox on 
<Re: [Nmh-workers] sync'ing an mh mailstore between two machines? > were:
=> tethys wrote:
=>  > --------
=>  > 
=>  > Peter Maydell writes:
=>  > 
=>  > >Just use rsync to copy the laptop's idea of the situation
=>  > >onto the desktop again? (And vice-versa in the morning.)
=>  > 
=>  > Bleurgh! It's a difficult problem to solve. Probably the best
=>  > way is to use a DVCS for your mail store. They're generally
=>  > explicitly designed for offline operation and resyncing of
=>  > the repository when you get connectivity again.
=>  > 
=>  > At this point, I couldn't really recommend anything other
=>  > than git, because it's the only one I'm aware of that tracks
=> 
=> well, this thread is certainly becoming more interesting than i
=> expected it to be.  certainly using git never would have occurred
=> to me.

Hmm...I'll need to look into git some more.

=> 
=> there's a very nice file tree syncing tool called "unison" that might
=> be useful as well -- i hadn't thought of it until peter mentioned rsync.
=> unfortunately it's no longer under active development, but in my
=> (limited) experience it works very well:
=>     http://www.cis.upenn.edu/~bcpierce/unison/
=> 
=> i'll have to think about whether it would be appropriate in this case.
=> 

IMHO, the problem with tools like unison & rsync for this task is that they are 
oriented toward content differences between files of the same name, and dealing 
with missing/added files.

The MH use presents a special case, in that we generally don't care much about a
file's name, but we care a lot about the content and directory where the file is
stored. In other words, I don't really care that the message that I am replying
to is in a file named "691". I don't ever expect the content of the message
associated with Message-Id <address@hidden> to change,
but I do expect the name of the file where that content is saved to change. In
the future, it may be in a file named 687, or 692. On the other hand, I do care
that the file is stored in ~/Mail/My-Lists/nmh. 

This means that tools like rsync will work very hard to resolve the internal 
differences between file ~/Mail/My-Lists/nmh/691 on my laptop and the 
completely different message with the same name stored on my desktop.

I really want to do some tests with the rsync option "--whole-file" to get 
around this problem, but I don't think that'll be sufficient, unless you can 
absolutely ensure that changes are never made on both machines...in which case 
the problem is trivial.

Mark


=> paul
=> =---------------------
=>  paul fox, address@hidden (arlington, ma, where it's 63.7 degrees)
=> 
=> 
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