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


Kern Sibbald wrote:
> 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.
>   

Absolutely.

> 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 
> magazine.
>   

That is the only real difference. It numbers "magazine" drives and 
forces a volume naming scheme based on magazine number and slot number. 
Basically, the files are named in a more human readable way, each drive 
has its own set of volumes, and the volume labeling can be automated 
using the 'label barcodes' command without requiring a separate barcode 
labels file. Otherwise, it works just like the disk-changer script from 
the 1.39 beta release.

> 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.
>   

This is being used in a couple of small production environments that I 
am affiliated with. One subtle thing to be aware of if using this method 
is that, like with real autochangers, it is necessary to issue a 'update 
slots' command in bconsole any time a magazine is changed. Has been in 
use for about a year with no real issues.

> 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.
>   

I find that this works really well, though if using multiple removable 
drives that are swapped in and out it is a bit of work to keep up with 
which volumes are on which drives. For this reason it is actually easier 
to manually label volumes and assign them to particular disk drives, 
though auto-labelling does work. I have used this for my home network 
machines quite a bit, and for small backup needs I highly recommend this 
method just for the sake of simplicity and low cost.

> Regards,
>
> Kern
>
>   
>> /ps
>>     
>
>
>
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