Zitat von Chris Adams <cmadams AT hiwaay DOT net>:

> Once upon a time, lst_hoe02 AT kwsoft DOT de <lst_hoe02 AT kwsoft DOT de> 
> said:
>> What about using more than one snapshot? If done right snapshots are
>> cheap, so you should have no problem to take a snapshot/mount per job
>> to get two jobs running. But i doubt you will gain much with parallel
>> backups on one filesystem/io-channel anyway.
>
> I'll have to check the space (not sure it is available right now).
>
> I do know that my old backup software did run the same backup (with
> parallel trees) somewhat faster (and that was to tape rather than disk).

If your client filesystem is slow it does not matter if you backup to  
disk or tape. Parallel backups on such filesystems only help if you  
don't saturate the io-channels of this filesystem because of CPU or  
other bottleneck.

>> Currently with VSS you have a limit of one job per windows machine
>> running, as we already find out :-(
>
> I thought that might be the issue.  I may be able to work around this by
> not using VSS for these particular trees, at least for testing.
>
>> But as said if you don't have independent io-channels or you are CPU
>> bound (data encryption) you won't gain very much by running more than
>> one job concurrently.
>
> I used multiple parallel trees with my previous backup software, in part
> because it seemed to have a high overhead with lots of files (one of
> these servers has a Maildir store with a couple of million files).
> Those backups did finish faster (as part of my overall network backup to
> tape) than my current test backups (just running a single job to disk,
> with an upgraded backup server and upgraded switches in-between the
> servers).  That's what got me looking at trying to run parallel jobs
> with Bacula (at least to test out the speed to see if it helped).

Backup software need to maintain metadata per file which create some  
overhead per file obviously. In case of Bacula this metadata are  
stored in the director database, so maybe you should have a look if  
this database is configured for high insert rate. If the database in  
question is at its max you will gain nothing by inserting in parallel  
with more than one job.

Regards

Andreas



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