On Mon, Jan 14, 2019 at 4:36 PM Erik Christiansen <dva...@internode.on.net> wrote:
> On 14.01.19 10:16, Chris Albertson wrote: > > Here are the classic failures: > > > > 1) You have a "backup drive" the mirrors all your data. SO after > > spending a few hours edits files yu save the file but the software has > > a bug and writes a corrupted file to disk. the yo "backup" the file > > and this over writes the only good copy of the file, the one you > > backed up yesterday. So not the file and the backup are corrupted. > > Solution: NEVER over write a backup. only save the CHANGES. You > > need to be able to go back in time and pull out the last working > > version > > In reality, there's always more than one way to eat an elephant, so > there's no real need to complicate life by making backups a growing > agglomeration of deltas¹. The nifty and very *nixy rsync utility solves > the write corruption problem directly. Rsync always verifies that each > transferred file was correctly reconstructed on the receiving side, You missed the point. The scenario is like this.. You have a file in the text editor window and you save it but unknown to you only there are 100 lines missing from the center of the file. Perhaps you ment to delete a word but accidentally deleted 100 lines. Perhaps the editor has a bug but in any case the file is corrupted on your main hard drive. Then you run "rsync" and it notices the time has been modified and writes it to the backup disk. Rsync does a nice job and checks the data is good. But in doing its job it has overwritten the only good copy of the file. The problem is that rsync overwrites old data with new data and violate the #1 rule about saving stuff which is "don't trash it." DOn't worry that a versioned backup system is complex. Today these run in the background and you never see how it works Funny how all the self-invented methods are EXACTLY what the professions did in the 1970's It works but a human operator has to "do stuff" the chance of human error or forgetting something is large. Now days it is set up with a few mouse clicks and "just works" and runs for years with not effort. > > -- Chris Albertson Redondo Beach, California _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
