Hi there,
Today I realized I hadn't sent this. It may have been overtaken by
events but here it is anyway...
On Sat, 11 Feb 2023, Christian V?lker wrote:
I have two clients which have a large share. These two (Debian) clients
sync this share on a daily base through rsync (through a third clientC,
but this should not make a difference). On clientA there is a cron job
doing rsync to clientC and on clientB there is a cron job doing rsync
from clientC. So in the end all three hosts have identical data. ...
BackupPC itself is only backing up host clientA so far (since months
now).? So the data is stored in /var/lib/backuppc.
Now I added the clientB share to BackupPC ... usage of the pool
increased approximately about the size of the share ...
You have missed some important information.
1. May we see does your BackupPC configuration files?
2. What is 'large' in 'large share'? Obviously adding an extra client
to the backup will produce a requirement for storage of a large amount
of metadata. Perhaps that's what you're seeing, although without more
information about data volume it's difficult to guess what's going on.
3. Do the files in the shares change? I presume that they do or there
would be no need to sync them, so that begs the next two questions
4. When do the files change? and
5. When do the backups take place?
Obviously if large numbers of the files change between backups and the
first backup takes place before the changes while the second backup
takes place after it, then you cannot expect deduplication to help.
* Is there dupe detecion on BackupPC?
Yes. We routinely back up just under 20 Terabytes of data from 12
hosts. After pooling and compression the pool size is 640 Gigabytes.
* If so, why does my pool size not decrease after a while?
* If by default it has to decrease, is there an explanation why it
does not on my host?
I do not know the answers to these questions. More information is needed.
Faced with this kind of situation I would investigate, in order to
(1) justify my trust in the numbers on which I base any conclusions and
(2) verify (if possible for a few, hopefully large, sample duplicated
files) that the physical storage location for the duplicated files on
the storage medium was the same - thus demonstrating deduplication.
--
73,
Ged.
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