Am Dienstag, den 18.07.2017, 10:21 -0600 schrieb Jason Bailey:
> I've got a mail server full of millions of tiny little files
> (messages) 
> that I back up to my Bareos server at another location. It works, but
> it 
> takes several days to complete, and I've had to use LVM snapshots to
> get 
> steady, consistent backups, as the data changes fairly rapidly from
> hour 
> to hour.
> 
> In total I've got around 1.2 terabytes of data spread across 18-20 
> million files that needs to be backed up to eliminate any possible 
> conflicts (uplink bandwidth on the switch during the day, for
> example).

This sounds like maildir mailstorage of cyrus imapd. If you're using
cyrus imapd, I wouldn't worry about snapshots at all. Just
reconstruct/repair (if they got messed up during backup - very
unlikely) and update them after a restore with cyrus tools.

> I'm trying to see if there is a way to configure Bareos so that
> there's 
> more efficient use of the bandwidth, or just find ways to speed the 
> whole process up. I've fiddled with setting the network buffer at
> the 
> bareos-sd level, enabling compression, enabling/disabling spooling,
> etc. 
> I'm getting10-15 MB/s at best, but looking uniquely at bandwidth
> alone, 
> I should see even better transfer speeds (network bandwidth is at
> least 
> 1 Gbps along the entire path).
> 
> Bandwidth between locations isn't an issue. From what I can see, the 
> excess overhead of transferring so many small files is what is
> causing 
> the majority of the slowdowns. Read speed from the disk (snapshot
> I'm 
> coping is riding off of an Areca RAID card) is 10-12 Mbps.

also turn off any kind of checksumming and other modification/access
time checking / comparing etc (avoid stat() calls). 
(In case of cyrus) just back up the databases and any new files. Once a
mail is there it's a file that will never change again - only vanish if
it gets deleted or moved.
  
Regards,
  Tom

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