rsync - Jun 2010 - --recursive and -H

Hello,

I have a question regarding using the --recursive option when preserving hard
link with -H.  How is it, that these two options are compatible when used
together?  I would think that RSYNC would need to see all files/inodes before
transferring, to preserve hard links.  But yet it still starts transferring
before reading the entire file list.

Don't get me wrong, this is excellent as there are 10's of millions of
files and it would take days and tons of memory to do it without the --recursive
option.  I'm just curious about if the large (15TB) backup I am currently
running is actually preserving hard links, or if I'm going to see in a few
days that it is not actually preserving them?

Thanks,
-Rob

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Rob Thompson, Systems Analyst
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Wayne State University
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On 26.06.2010 09:01, Rob Thompson wrote:
> 
> Hello,
> 
> I have a question regarding using the --recursive option when 
> preserving hard link with -H.  How is it, that these two options are 
> compatible when used together?  I would think that RSYNC would need to 
> see all files/inodes before transferring, to preserve hard links.  But 
> yet it still starts transferring before reading the entire file list.
That's easy.

'stat'ing a file also gives it's inode-number and the link-count
(number
of directory entries).

When you have link-count == 1 there is nothing special to do.

When you have a link-count > 1 you can discard the data as soon as you 
transferred as many files, with the same inode, as the link-count says. 
Of course the discarding only works as long as all hard-links are inside 
the directory-subtree you are transfering, otherwise rsync keeps piling 
up memory, at least i'm pretty sure that rsync works that way.



Bis denn

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