[Dovecot] prevent dovecot from modifying maildirs

[Joseph Tam]

> In order to save space I prefer no to have such half-files (mails) ,
> and it is for this reason that I am asking if there is any way to
> prevent this. 
> 
> I'm not an expert in field of file systems, so I can be asking very
> naive questions...  but I appreciate your comments on this topic.

Filesystem consistency is different than, for lack of a better term,
dovecot consistency.  The latter places additional constraints on the
content of files, rather than treating them as sequences of disk blocks.

I don't think you can ensure the latter without stopping all dovecot
processes (and maybe the MTA/LDA as well), which will be much more difficult
and disruptive than just taking a snapshot.

(I think some snapshot aware application like databases and hypervisors
allows the operator to put the application in a state of acquiesence,
long enough to take a snapshot, then unblock all processes after the
snapshot.)

I'd take the suggestion of the previous poster: take snapshots, don't
worry, be happy.  The small amount of inconsistencies is trivial compared
with quickly recovering a mail store after disaster.

Joseph Tam <jtam.home at gmail.com>