Well, thanks for the inputs on this.
I can gladly report that when I go to the trouble of
restoring two subdirectories of the directory I tarred with Amanda
( each about half a gig ) to a temporary location, a 'du -sk' reports
the exact same size for the original and restored subdirectories. This
is good news and makes me feel confident that tar ( version 1.13.17 ) and
Amanda are doing what I hope they are. :)
Paul
->>In response to your message<<-
--received from John R. Jackson--
>
> >... I have noted that the amount of
> >data backed up as reported by Amanda, though very close in size, is
> >consistently a bit less than what 'du -sk' reports. This is a bit
> >disturbing. One always wants to see the backup image, if not be exact,
> >be at least a bit larger in size than the source image. Can anyone
> >offer an explanation for this, ie. should I be concerned?
>
> Three things come to mind. One is files with "holes", i.e. a file with
> a size larger than what is physically allocated, such as the DBM files
> for the E-mail aliases. The "du -sk" may or may not be taking those
> into account.
>
> It also may or may not take into account files with multiple links.
> For instance, it may double count a file with two links that tar detects
> and only backs up once.
>
> The third (and probably best) possibility is that tar writes files in
> units of 512 bytes. So if you have lots of short files (or lots that
> fall in the lower half of 1 KByte boundaries), they will take less space
> than rounding up all the sizes to KBytes.
>
> >Paul Yeatman
>
> John R. Jackson, Technical Software Specialist, [EMAIL PROTECTED]
--
Paul Yeatman (858) 534-9896 [EMAIL PROTECTED]
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