How does Backup actually work -- files selected, best approach, etc.

I am not very knowledgeable on the LINUX environment and heritage. My question has to do with what backup method to select and how to parameterize.

Windows centric folks may have some difficulty in understanding the ReadyNAS backup options – at least this Windows centric fellow. I will attempt to outline my confusion. Any help would be very useful.

Typically in the Windows world (business system environment) everyone is familiar with the concept of a Backup Job and the notion that backups come in ‘sets’ that represent the initial backup and then a form of differential or incremental backup from the base set. A set can span multiple backup events (either differential or incremental) and then the process cycles around to start again. Typically there is a notion of several backup sets being saved so there is a reasonable timeframe for data recovery of files. This cycle of removing older sets is typically referred to a purging.

The ReadyNAS firmware documentation uses the term ‘protocol’ regarding the backup process. I believe that refers to the transport level methods and not the backup selection process of files to be transported. Is that true??

Against that background here are the questions that puzzle me – others may be confused as well.

• Windows/NAS(Timestamp) – apparently refers to a backup protocol independent of the transport method. It relates to incremental backups. What is the selection algorithm for a file to be in the incremental backup set? Is there only one incremental backup produced and older incremental backups are then overwritten? One party has indicated that this method is a copy from source to destination with no icrements but I may have not understood properly. The firmware documentation indicates (ReadyNAS OS 6.2, page 199 ) talks about incremental backup. Which is currently correct??
• Windows (Archive Bit) – apparently refers to a backup protocol independent of the transport method. It is covered in the 6.2 firmware manual. This option is absent from the 6.4.0 software. Is this a mistake or intentional?
• FTP – my view is that this would refer to a transport protocol and includes the typical client/server FTP commands. What is the selection algorithm for a file to be in the incremental backup set? Is there only one incremental backup produced and are older incremental backups are then overwritten?
• NFS – my view is that is a transport protocol for distributed file system but it most likely has more robust capabilities. What is the selection algorithm for a file to be in the incremental backup set? Is there only one incremental backup produced and older incremental backups are then overwritten?
• Rsync Server – seems to be a robust method of source/destination synching. As far as I can tell, the data to be selected is in the backup definition and the Rsync protocol offers a selection method plus allows files to be removed from the destination if they are removed from the source. What is the selection algorithm for a file to be in the incremental backup set? Is there only one incremental backup produced and older incremental backups are then overwritten? Will it work for intra-system backups, e.g. to a different volume on the same ReadyNAS device?
• Rsync over Remote SSH – seems to be a robust method of source/destination synching using the SSH capability/transport mechanism that offers substantially more security. As far as I can tell, the data to be selected is in the backup definition and the Rsync over Remote SSH protocol offers a different and more secure transport mechanism.

In summary, I am looking for precision regarding what is selected and copied along with a notion of how the incremental capability works.  Additionally the question of whether there are file differences based on the transport method is importan as well.