HAMMER history friendly backup tool

[Predrag Punosevac]

Bomrek Koganvutram <232.20711 at chiffre.aleturo.com> wrote:

> * Predrag Punosevac on Tue, Mar 15, 2016 at 07:02:06PM -0400:
> > It looks increasingly unlikely that I will get any suggestions to the
> > original question so I am just going to post my own "solution" to the
> > original problem.
> 
> > I remember that after Unison sync the file history was lost. What I
> > didn't remember until today was that Peeter noticed that the same was
> > true with rsync 
> 
> > https://marc.info/?l=dragonfly-users&m=135885584004499&w=2
> > 
> > which indeed shares the main algorithm with Unison.  He also noticed
> > that using scp or even a cp over NFS (my observation which is fully
> > tested) will play well with HAMMER history. So long story short it would
> > be fairly easily to cook up such a backup tool which will traverse the
> > on my home directory (running OpenBSD) and just cp the files which have
> > changed since the last run. I also tested rdiff-backup if anybody cares
> > and the result is the same as with rsync and unison.
> 
> Your post is now somewhat dated, but just in case:  Have you tried using
> ???--inplace??? with rsync?  My guess is that it???s the way how rsync and
> similar tools create their files that breaks HAMMER history:  Instead of
> overwriting the file, it is replaced by a new file.  Since it???s a -new-
> file, a new history will start there.
> 


You are completely correct! I can confirm that using switch 

--inplace

in with rsync will preserve HAMMER history. That is brilliant. 


> With ???--inplace???, rsync instead overwrites the original file (which has
> all kinds of drawbacks, that???s why it isn???t the default), but for your
> use case perhaps it???s worth a try.
> 

I understand that but rsync is not designed when advanced file systems
like HAMMER were available. I am too tired to analyze draw backs of
--inplace switch but my feeling is that they probably don't apply to
HAMMER as a target.

> > I remember that after Unison sync the file history was lost. What I
> > didn't remember until today was that Peeter noticed that the same was
> > true with rsync 
> 
> I have used Unison a few years back, and it -does- use the same
> replace-with-new-file-approach, pretty much for the same reasons.
> 

It also uses the same algorithm as rsync. However I have not being able
to find the unison switch which will allow me to accomplish the same
thing I did with rsync. Anybody who is more familiar with unison? What
is the equivalent of --inplace switch? 

> > Personally I decided to run HAMMER snapshot as a cron job after rsync
> > and in that way preserve the older version of files. 
> 
> That would have been my second suggestion; it may not be as convenient
> as ???undo???, but at least the data is known to be preserved.
> 
> 
> Sorry for the late answer; I flagged it a few weeks ago, but then work
> got the better of me and I completely forgot.??:o)
> 
> 

You are forgiven :) You made my day with this clever observation.  As a
bonus I am posting a link to an interesting post about backup solutions

https://www.reddit.com/user/rsyncnet

As smart as that post is (apart of the fact that he is mostly talking
about non-enterprise backup so there is no mentioning of Amanda, Bacula,
ZFS replication, HAMMER mirror or even a tarsnap) the very first
paragraph is just wrong

"The simplest thing to do is to rsync from one system to another. Very
simple, but the problem is it's just a "dumb mirror" - there is no
history, no versions in the past (snapshots in time) and every day you
do your rsync, you risk clobbering old data that you won't realize you
need until tomorrow."

at least it is wrong if your your rsync target is DragonFly NAS
appliance as cleverly observed by Mr. Bomrek. I just wonder where does
the glastree fit into all this story?

http://old.igmus.org/code/


Best,
Predrag

> Cheers,
>     Bomrek
> 
> 
> -- 
> Was wir brauchen sind ein paar verr??ckte Leute
> -- seht euch an, wohin uns die Normalen gebracht haben.
> 		-- George Bernard Shaw