[Info-vax] BACKUP, rsync, Time Machine (was: Re: Re; Spiralog, RMS Journaling...)

[lawrencedo99 at gmail.com]

On Tuesday, June 21, 2016 at 1:13:49 AM UTC+12, Stephen Hoffman wrote:
> On 2016-06-20 10:13:41 +0000, Lawrence D’Oliveiro said:
> 
>> rsync basically answers the question “given a source directory «src» 
>> and a destination directory «dst», what is the minimum that needs to be 
>> done to the contents of «dst» to turn it into an exact copy of «src»?”
> 
> Which is only part of what Time Machine does.  You're obligated to 
> maintain multiple rsync targets, if you want any depth to your backups.

I have a script to do that. Backup run twice a day for one client, going back a week. (This is separate from the backup service provided by the central IT department.)
 
>   Time Machine functions more like a VCS here, in that a single target 
> contains anything from a single version of the source to months or 
> years of source file changes, with file, directory or everything 
> restorable by time.

That’s what those “multiple rsync targets” provide. Each is just a separate directory.

> Time Machine also avoids storing multiple copies 
> of unmodified files, where using multiple rsync targets would require 
> the storage system to do that de-dup.

rsync avoid storing multiple copies of unmodified files, like I said.