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Re: [Bacula-devel] backup to removable external disk

On Wednesday 10 September 2008 20:01:59 Peter Sjoberg wrote:
> On Mon, 2008-09-08 at 14:51 -0400, Dan Langille wrote:
> > See also:
> >
> > http://tregnago.blogspot.com/2008/09/bacula-with-usb-disks-vchanger-alter
> >ed.html
> This script definitely looks like the path to take. Did a quick trial
> implementation and it works as documented - it's just that I need
> something a little different.
> Biggest issue is that this script handles a single USB connection (per
> storage device) and I want to use two. Each disk is considered one
> magazine filled with a pile of tapes and I have to change that
> "magazine" now and then to avoid it filling up (or when it complains
> that it's full).
> Looked at disk-changer script and a quick glance it seems to do
> something similar, talks about diskfiles as slots.

One note about disk-changer is that it is officially supported with Bacula 
because it is *very* heavily used in our regression tests both for disk tests 
and for our virtual tape tests.  We know it works.

The functionality of disk-change is probably a bit less than the vchanger 
script you mention because disk-changer does not have the notion of a 

I have never used disk-changer in a production environment, but if I were 
re-implementing the system documented in the manual in the "Automated Disk 
Backup" chapter (which is by the way still running), I would use the 
disk-changer script.

> I will think about it a bit but the way I feel I want it done is to have
> another level between and the easiest way to do that is probably to move
> everything up one level.
> I have single "drive" that has a "magazine" with two "slots"/"tapes".
> Then each tape is really a physical disk with one big file on it.
> This way, when one disk/tape is filled up it should automatically move
> to next tapedisk and at some point I can replace the filled tapedisk
> with an empty one.
> One issue I see with this is that I would end up having a single 1T file
> on each disk and I don't think that's to good so I'm still open for
> suggestions.

The advantage of the "Automated Disk Backup" chapter scheme, or the vchanger 
script, or disk-changer script is that each volume has a maximum fixed 
reasonable size.  With the virtual changer scripts, you simply create as many 
Volumes you want each in a different slot, and limit them to some maximum 
size.  Bacula will then manage them.  If you setup a prunning algorithm as 
described in the "Automated Disk Backup" chapter, it then automatically 
manages everything. 

Life becomes a bit more difficult if you want to swap out USB drives.  In that 
case a virtual changer such as vchanger that has a concept of magazines may 
be useful.

Also, you should know that if a File device is marked as removable, Bacula 
will search the device looking for Volumes.  In theory, if you configure 
Bacula correctly, you can just plug and unplug USB devices (providing Bacula 
is not writing to one) at any time, and Bacula will figure out what Volumes 
are available.  This has never been extensively tested though.  This only 
works if you are doing something like the "Automated Disk Backup" and not 
using one of the virtual autochangers.



> /ps

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