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Re: [Xen-users] Backup domU

To: Rainer Sokoll <rainer@xxxxxxxxxx>
Subject: Re: [Xen-users] Backup domU
From: Andrew McGlashan <andrew.mcglashan@xxxxxxxxxxxxxxxxxxxxx>
Date: Sat, 09 Jul 2011 23:44:48 +1000
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Rainer Sokoll wrote:
Am 09.07.2011 um 12:17 schrieb Andrew McGlashan:

The only issue with rsync with rsnapshot from what I can see, is for very large 
files that change frequently.  You might end up having loads of copies of these 
large files and that would be painful in terms of storage and transfer.  Take a 
2TB Oracle datafile for instance; don't want to touch that right now with this 
method, but Oracle has other backup methods anyway .....

Yes, rsnapshot does deduplication by using hard links. This is file based 
deduplication; what we really want is deduplication on block level, like e.g. 
ZFS does.
For Linux, I came across lessfs (http://sourceforge.net/projects/lessfs/files/).
Anyone here who can provide experiences with lessfs?

If the file name changes whilst none if it's content does ... or the file's location changes, then rsnapshot doesn't de-duplicate those files. Even files that are very slightly modified mean a whole new copy of them is created (no hard link). Of course the old copies that are no longer on the system being backed up will "age out" via the cycling of rsnapshot directories over time.

Kind Regards

Andrew McGlashan
Broadband Solutions now including VoIP

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