BackupPC-users

Re: [BackupPC-users] restore questions

2009-01-19 13:54:14
Subject: Re: [BackupPC-users] restore questions
From: Les Mikesell <les AT futuresource DOT com>
To: "General list for user discussion, questions and support" <backuppc-users AT lists.sourceforge DOT net>
Date: Mon, 19 Jan 2009 12:51:51 -0600
Nick Smith wrote:
> So is the way im doing it now going to work if i need to do a restore
> down the road?
> Would doing full backups be better than incrementals?

Fulls are better. They take more time because the file is read for the 
checksum comparison but they don't take a lot more bandwidth.  And 
depending on your settings, incrementals may transfer all differences 
since the last full so as you accumulate new files they will keep taking 
longer.

>>>From what your saying it sounds like the full backups are actually
> doing incrementals?
> Or is it because most of the files are already in the pool so it just
> does a hardlink instead?

The transfer and storage are two different concepts.  Rsync transfers 
only the differences from the existing previous full run.  Storage links 
all files with identical content to a common pool instance.  To 
understand the difference, consider that a full tar or smb backup would 
transfer all of the content but end up with the same storage archive.

> If i tell it to only keep 1 full backup and only do a full every 6
> months, once it does the next
> full backup does it change the hardlinks to point to the latest full
> and remove the first? or
> does it keep the initial full just to keep the hardlinks in working order?

Hardlinks are never 'changed'.  Pool copies are made using a hash of the 
file contents so duplicates can be found quickly.  New content becomes a 
new entry.  New matches become new links.  As old backups expire, the 
link count on the pool copies may go down to 1, meaning that no current 
backup links to it, and the nightly job will then remove it from the pool.


-- 
   Les Mikesell
    lesmikesell AT gmail DOT com


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