[Box Backup] Issue with Incremental backup of mail folder

[Imran Niazi]

Hey guys,

I'm running 0.10 of server/client, and I ran into an issue.  One of the
machines that the client runs on is the mail server, and of course backing up
/var/spool/mail (mbox format large file that stores all the messages for a
particular user). 

Anyway, all the emails of a particular user were deleted, approximately 8 days
ago.  I thought I could get into atleast an one or two old backup of that
folder, but the file only shows once, and its about 24 hours old (I assume its
still under MaxUploadWait.  I assumed that we would be able to get to an older
version of a file, but it would also mean there would be as many versions of
that file as there would be days.  But It also means that if a file is
truncated , we have no backups of the file.  

Or I'm hoping there is a low level way of finding out previous versions of the
file and possibly un-diffing the file?  I guess the way it works is, that
since the inode didn't change, the backup thinks that all modifications are
the same file and the original can be discarded (or maybe the client behaves
like that?)

I guess if its not possible to get the old versions, then it would be cool to
have it such that a user can specify a certain date & time, and the backup
would give you the state of a file at that time.  Also there would be an
option to give a time range, where if a file changed after the time spcified,
but still in the time/date range.  To do this functionality, however, you'd
have to track a timeline plus diffs for each file.  There would be a
resource/info file for each file tracked/backedup, that would list the initial
date of backup, the date the next backup ran, and the diff of it.  If the
space requirements are going to be very large for this feature then there
should also be a configurable number of days/months that it keeps this state
information.  In its housekeeping, it will remove the deltas from earlier than
those days, and update the initial state be the state on that date, as well
change the 'initial date' in the resource/info file.

Anyway, i'm quickly thinking out loud, and there might be a big flaw in my
thinking.  

It would be an important feature, I believe.  Of course if this is how its
done already, then I probably wasted everyone's time reading this email.  :)

Imran Niazi