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Re: [Bacula-devel] Optimizing disk based backups


On Friday 23 May 2008 20:31:09 Michael Short wrote:
> Hello,
>
> I realize that Bacula was originally developed for tape based backup
> systems, but disk space is becoming more inexpensive everyday. It is
> cheaper and more reliable to maintain a system which uses disk based
> mediums to store backup data. The problem is that disk based restores
> are unnecessarily slow, due to the linear nature of the backup
> volumes.

You are probably running with an old version of Bacula because disk based 
restores even with monster files are lightning fast because they use lseek().  
I forget in which version this was implemented, but it seems to me was 2.2.0

>
> I am addressing this problem because at some point it would be
> necessary to access old backup archives should anyone implement an
> rsync or xdelta type enhancement for Bacula. Perhaps instead of
> storing individual file locations in the catalog,

Bacula does not store individual file locations in the catalog.  It stores 
what one might call check points or seek points.

> an index of the 
> backup could be stored at the beginning or end of a volume, 

Bacula already keeps indexes of the backup in the catalog, so there is no need 
to store it on the volume.

> so that 
> unnecessary "forward spacing" would no longer be needed for disk based
> volumes. This extra would also make the process of recovering catalog
> information from volumes much less painful.

Bacula normally optimizes forward spacing, and on disk volumes (version 2.2.0 
and greater) a "forward space" is essentially instantaneous -- no I/O 
involved simply an lseek() call.  Without "forward spacing" Bacula would be 
unable to restore files, so I am not sure I see your point unless you are 
using an old Bacula version where it sequentially reads the volume to effect 
forward spacing.

>
> Just a suggestion..
>

Regards,

Kern



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