Re: [rdiff-backup-users] rdiff-backup vs. rsync(d) at the remote end

[devzero]

Hello again, 

i have probably found an intersting solution for doing rdiff-backups via rsync 
with local mirror and without needing twice the space as usual.

i`d like to discuss this solution and getting some feedback. 

if it`s a good and reliable solution, maybe it`s useful for others, too.

the trick for saving the diskspace for rsync mirror is using the rsync option 
"--link-dest",whis is set to the rdiff-backup repositroy. --link-dest means, 
that rsync can store data space-efficiently by creating hardlinks. hardlinks 
are created whenever the rsynced file already is at another destination. so if 
the rdiff-backup directory contains exactly the same file which is being 
rsynced, then rsync can detect this and create a hardlink instead. files which 
changed or which are new are just rsynced as usual. for me this saves most of 
the space the rsync directory normally needs.


this is my current backup script (i simplified it just to show the essential) :

------------
cd /backup

rm -rf hostA_rsync

mkdir hostA_rsync

rsync -az -H --link-dest=./hostA_rdiff  hostA:/ ./hostA_rsync

rdiff-backup --no-hard-links ./hostA_rsync ./hostA_rdiff
------------


for my curiousity i needed to add --no-hard-links to rdiff-backup, otherwise 
rdiff-backup behaved strange with this.

see the difference:

before:

du -s -k hostA*

30014511  hostA_rdiff
24219719  hostA_rsync

after (made a second hostA_rdiff for testing - this is why it is smaller):

du -s -k hostA*

24243554  hostA_rdiff
219719      hostA_rsync


since i just have found this solution and didnŽt test in depth (maybe there are 
problems?) , i`d glad to hear some comments about this.

regards
roland



------------------------------------------


        Betreff:         Re: [rdiff-backup-users] rdiff-backup vs. rsync(d) at 
the remote end
        Von:     "roland" <address@hidden>  ins Adressbuch
        An:      "Gerard van Dijnsen" <address@hidden>
        Cc:      address@hidden
        Datum:   24.06.06 16:03:31


hi!

mhhh - still wondering here and spending thoughts over and over again...

> As far as I can see, there are a lot of reasons for using a server on
> the receiving side.

yes - but why does this need rdiff-backup as server? rsync can run as a
server, too.

>One of them is storage of metadata, the most
> important however is keeping a history using 'reverse' diffs.

mhh - but metadata is only stored on the backup-machine within the
rdiff-backup repository.
nothing on the client side. rdiff-backup just pulls the data and metadata
from the backup client.
whatever data/metadata rdiff-backup needs on the receiving side for storing
this - an rsync
daemon on the remote site should be able to "deliver" this (imho - in
theory).

does somebody have a clue what's different "on the wire" between rsync and
rdiff-backup ?

itŽs gets a bigger problem for me, because i cannot install rdiff-backup on
many remote machines and
so i need to create a local copy via rsync and rdiff-backup'ing it
afterwards.
this doubles storage and isn`t very optimal.

ok, i know that i can convert a rsync mirror with "-b --force" into a
rdiff-backup repository - but
i`m not allowed to rsync afterwards.

>Actually, take a look at Duplicity and you will see a nice example of what
>you are looking for.
thanks. maybe , fusessh is also worth looking at....

regards
roland


----- Original Message -----
From: "Gerard van Dijnsen" <address@hidden>
Cc: <address@hidden>
Sent: Saturday, May 27, 2006 6:45 PM
Subject: Re: [rdiff-backup-users] rdiff-backup vs. rsync(d) at the remote
end


> As far as I can see, there are a lot of reasons for using a server on
> the receiving side. One of them is storage of metadata, the most
> important however is keeping a history using 'reverse' diffs. This might
> be implemented differently using rsync perhaps, I am not sure. Actually,
> take a look at Duplicity and you will see a nice example of what you are
> looking for. You only need ssh on the receiving side for this to work...
>
> Gerard
>
> On Sat, 2006-05-27 at 13:24 +0200, roland wrote:
>> Hello !
>>
>> while thinking about (and digging into) how rdiff-backup is working
>> internally, i wonder a little bit about rdiff-backup being needed at the
>> remote end.
>>
>> wouldn`t rsync(d) be sufficient for this (in theory) ?
>>
>> i`m asking this, because it's a lot easier and more "lightweight" to
>> install
>> rsync(d) on the clients you need to backup.
>>
>> regarding "what's being transferred over the wire or being done at the
>> remote end" - can someone explain the difference between rdiff-backup and
>> rsync and give a comment about possible replacement of rdiff-backup with
>> rsync(d) ?
>>
>> regards
>> roland
>>
>> ps:
>> actually, i even have one machine i need to rsync first to a local
>> directory
>> and rdiff-backup from that, because i'm not allowed to install python on
>> that machine. so this takes twice the space on my backup machine.
>>
>>


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