On Sat, Apr 7, 2012 at 7:49 PM, Alexander, Clint Mr ARMY GUEST USA
USAMC USA <clint.alexander AT us.army DOT mil> wrote:
>> Rsync needs the -H option to recreate the hardlinks.  There are some
>> practical limits to the size of a pool that can be copied in a
>> reasonable amount of time because identifying and recreating the
>> hardlinks is somewhat inefficient - and you have to include the entire
>> tree in one pass for it to work.
>
> I found this as well (even though most instructions give the archive mode
> (-a) without the hard-link switch).
>
>
> What about the requirements of the two directory structures:
> __topdir__/data/pc & __topdir__/data/cpool

That's where the hardlinks that provide pooling happen.   They must be
in the same filesystem.

> If I only copy the "pc" directory to another server, I noticed that my new
> installation of BackupPC apparently reads it just fine and displays the
> previous full and incrementals that we've collected over the years.

The copies that are made only to the pc directory won't be shared.
Depending on how you copied them, they may still have the hard links
to each other, but they need the cpool link if you want to be able to
match up the content on new backups.

> The
> backuppc service seems to look for existence and ownership of "cpool", but
> does not complain that it is empty (which it is in my test environment).
>
> Do we really need the cpool directory? Will backuppc rebuild this in some
> way?

If you use rsync, new backups will make hardlinks to files where the
names and content match the reference backup, but these won't be added
back to the pool.  And if you add new targets, their files will make
links into the pool, but these will continue to be separate instances
from the ones you copied under /pc/ without the pool links.
Everything should actually work correctly, but you'll never regain the
space until all of the copied backups expire.

-- 
    Les Mikesell
      lesmikesell AT gmail DOT com

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