Re: Linux 2.6.29

[Andreas T.Auer]

On 01.04.2009 14:53 Chris Mason wrote:
> On Wed, 2009-04-01 at 10:55 +1100, Dave Chinner wrote:
>   
>> If you crash while rsync is running, then the state of the copy
>> is garbage anyway. You have to restart from scratch and rsync will
>> detect such failures and resync the file. gnome/kde have no
>> mechanism for such recovery.
>>     
> If this were the recovery system they had in mind, then why use rename
> at all?  They could just as easily overwrite the original in place.
>   

It is not a recovery system.  The renaming procedure is almost atomic
with e.g. reiser or ext3 (ordered), but simple overwriting would always
leave a window between truncating and the complete rewrite of the file.

> Using rename implies they want to replace the old with a complete new
> version.
>
> There's also the window where you crash after the rsync is done but
> before all the new data safely makes it into the replacement files.
>   

Sure, but in that case you have only lost some of your _mirrored_ data.
The original will usually be untouched by this. So after the restart you
just start the mirroring process again, and hopefully, this time you get
a perfect copy.

In KDE and lots of other apps the _original_ config files (and not any
copies) are "overlinked" with the new files by the rename. That's the
difference.

Andreas

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