LVM snapshots vs. --link-dest

Andrew Gideon c182driver1 at
Mon Sep 28 08:18:55 MDT 2009

On Sun, 27 Sep 2009 17:14:42 +0000, Andrew Gideon wrote:

> I was thinking that an alternative to links, which do nothing to
> preserve space when small file changes have been made, would be using
> LVM snapshots.  Instead of creating a new directory for a new backup,
> and specifying --link-dest to the previous directory, I'd create a
> snapshot of the current backup volume to preserve it, and then do a
> normal (ie. w/ o --link-dest) rsync to the "live" volume for the new
> backup.

I've been thinking a little more about this.  It assumes that --inplace 
actually does what it sounds like it does: it modifies only the disk 
pages of a file that have changed, as opposed to changing the entire file 
or creating a new file or some other thing which causes the file to 
"move" on disk.

Does --inplace do what it sounds like?  I was reading a dialog from 2004 
which claimed that adding this to rsync would be tough.

The --update option is also useful in this regard?  What would happen if 
--inplace were used but --update were not?



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