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On 12/02/2015 01:36 PM, Jon LaBadie wrote:
| On Tue, Dec 01, 2015 at 10:28:27PM +0000, Debra S Baddorf wrote:
|> I agree with Alan’s comment.   You shouldn’t need   - - notaper.
|> (But you CAN use it

Thanks all, I think I understand now.  It's a bit more subtle than
understanding Amanda config (which I don't yet!)

The filesystem to be backed up consists of 9 directories, where almost
every file is hard-linked into the other 8 directories.

[It's daily backups and incrementals, where if the file is unchanged,
it's hard-linked to the other identical copies.]

While df and du both show the backup to be 990Gb, a naive view (not
taking into account hard links) shows it at over 7Tb.  The Amanda size
estimator shows 7Tb (via amstatus), not 990Gb, hence, it's way too big
for my 1.5Tb holding area.  Web searches on the subject seem to
indicate that the Amanda backups _will_ preserve hard links (hence
only backing up 990Gb), so if I let the backup run, it would have
worked (but shoe-shined unacceptably).  On a faster drive, the
shoe-shine wouldn't have mattered, but it would have bleated about not
having enough tapes (even tho it wouldn't use them).

To get around this, I tar'd it to a file (result just over 1TB), which
Amanda was perfectly willing to copy to holding area (albeit not
necessary in this case), and then stream to the drive.  Annoying -
extra steps and extra tar wrapping - would be nice if the estimator
got it right.

I've not dived into the Amanda planner/estimator code, is it possible
for it to take into account hard links?

[If it required coding, potentially it's simple: by making the
assumption that every target of a hard link is going to be backed up
in the same run, so you could divide every file's size by it's link
count.  Otherwise, you have to do the accounting that du/tar/rsync does.
]
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