Matthias Meyer wrote:
> 
>> Since version 3.0.0 (protocol 3 on both ends) rsync uses an
>> "incremental" mode to generate and compare the file lists on both sides.
>> So memory usage decreased a lot, because just a small part of the list
>> is in memory all the time. But the massive hardlink usage of BackupPC
>> causes very slow copying of the whole structure, because link creation
>> on any filesystem seems to be a very expensive task (locks?) ...
>>
> 
> So it seems possible to make the initial remote backup by dd and after this
> a daily rsync?
> Because on a daily basis are (hopefully) not tons of new hardlinks which
> have to be created on the remote side.

Rsync still has to traverse all of the pool/pc trees in one pass to 
match up the links by inode number so there is some limit relative to 
the RAM on the machine to what it can reasonably handle.  But with the 
new protocol 3, that limit might be fairly large.

>>> In my opinion dd or cp -a isn't possible too because they would copy
>>> all the data. That would consume to much time if I syncronize the
>>> locations on a daily basis.
>> Any other tool has the same time consumption if it keeps hardlinks
>> ("cp" e.g. does that with option "-l").
>>
>> A somehow "lazy" solution would be to just copy the "pool"-Files (hashes
>> as file names) by "rsync" and create a "tar" archive of the "pc"
>> directory.
> 
> I would believe that creating of the tar archive and copying it to the other
> location will consume nearly the same time, space and bandwidth as dd or
> cp. Isn't it?

The BackupPC_tarPCCopy utility makes a tar image containing only the 
link information, assuming that you have already copied the pool, but 
yes it does take a very long time to complete a restore.  However, as a 
disaster backup it might be useful.  The down side is that you'd need to 
both rsync the pool and complete the BackupPC_tarPCCopy run with no 
changes to the master server.

-- 
   Les Mikesell
     lesmikesell AT gmail DOT com




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