Re: convert old full + differentials into new full

On 17/04/2021 20:11, imschmeg wrote:
> On Fri, 16 Apr 2021 21:39:24 +0200
> Denis Corbin <[email protected]> wrote:
> 
>>
>> Or maybe making a mix, having several raw of incremental (I) backups
>> based on the same full (F) backup, (D standing for an incremental
>> based on the full thus a "Differential" backup):
>>
>> F+D-I-I-I-I
>>  |
>>  +D-I-I-I-I
>>  |
>>  +D-I-I-I-I
>>
>> F+...
>>
>> There is no best solution for all cases, it always depends on the
>> context/environment/"data life".
>>
> 
> I think I have a better solution for my purposes: use rsync to update
> an off-line, possibly remote mirror of the sources quickly, then use dar
> to archive that mirror to slow secondary storage. 

Yes, rsync+dar is an option. Though I'm not sure of what advantage it
will bring here, as you do not use compression nor encryption, dar will
not drain more CPU resource than rsync. It may however drain more
virtual memory (RAM) than rsync depending on the number of files to backup.

You can also create the backup directly on the remote host in a single
dar command:

dar -c sftp://login@host/path/where/to/store/backup ...
more details in man page

Both ways are possible (dar with embedded sftp / dar + rsync), have each
their advantages and drawbacks you have to consider on your particular
case.

The following benchmark can also give you some insight to find the best
match for your particular case:
http://dar.linux.free.fr/doc/benchmark.html


> I don't have to
> worry too much about the speed at which I can rescue the most recent
> backup from dar, since the rsync mirror serves that purpose.  Also, the
> on-line-intrusive operation is an incremental rsync update of the
> mirror, which is fast (provided access to the mirror is fast, of
> course).  Hence I don't have to worry about doing an occassional slow
> and intrusive large dar differential backup.  This solution requires
> more storage, but probably is the least intrusive of on-line
> operations.  I also get to choose whether to have the rsync mirror and
> dar archive be remote or just the dar archive be remote.  That depends
> on the network speed vs. local disk speed and availability, as well as
> the safety of having the mirror local vs. remote.
> 
> 
> 


Cheers,
Denis