Erkennung differentielles back-up von 1:1 ausgetauschten Daten

[brakeprofi]

Ich hab eben folgendes gemacht, mir ist in meiner FLAC CD Sammlung auf der DS ein Lied aufgefallen, welches wohl nicht korrekt von der CD gelesen wurde.
Ich hab dann eine neue Version über die defekten Lieder drüber gebügelt, welche ja gleichen Namen, Dateigrößen usw. weiter haben. Jetzt war ich am überlegen, ob ein differentielles back-up das überhaupt erkennt Am Erstellungsdatum ?

 

[jahlives]

Wahrscheinlich am Inhalt. Das Backup wird wohl auch Dateihashes verwenden und damit erkennen wenn auch nur ein Bit der Datei geändert wurde

 

[itari]

Die Beschreibung von rsync sagt hierzu:

Rsync finds files that need to be transferred using a lqquick checkrq algorithm (by default) that looks for files that have changed in size or in last-modified time. Any changes in the other preserved attributes (as requested by options) are made on the destination file directly when the quick check indicates that the file's data does not need to be updated.

Es gibt auch die Option --checksum. Hierzu die Beschreibung:

This changes the way rsync checks if the files have been changed and are in need of a transfer. Without this option, rsync uses a lqquick checkrq that (by default) checks if each file's size and time of last modification match between the sender and receiver. This option changes this to compare a 128-bit MD4 checksum for each file that has a matching size. Generating the checksums means that both sides will expend a lot of disk I/O reading all the data in the files in the transfer (and this is prior to any reading that will be done to transfer changed files), so this can slow things down significantly.

The sending side generates its checksums while it is doing the file-system scan that builds the list of the available files. The receiver generates its checksums when it is scanning for changed files, and will checksum any file that has the same size as the corresponding sender's file: files with either a changed size or a changed checksum are selected for transfer.

Note that rsync always verifies that each transferred file was correctly reconstructed on the receiving side by checking a whole-file checksum that is generated as the file is transferred, but that automatic after-the-transfer verification has nothing to do with this option's before-the-transfer 'Does this file need to be updated'-check.

http://linux.die.net/man/1/rsync

Itari