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Re: [Bacula-devel] Trying out the virtual disk changer feature.


Graham Keeling wrote:
> On Fri, Oct 17, 2008 at 05:54:05PM +0200, Kern Sibbald wrote:
>   
>> On Friday 17 October 2008 17:37:00 Graham Keeling wrote:
>>     
>>> Hello,
>>> Going back a couple of months, there was this short exchange:
>>>
>>> On Fri, Aug 15, 2008 at 10:49:50AM +0200, Kern Sibbald wrote:
>>>       
>>>> On Friday 15 August 2008 10:36:36 Graham Keeling wrote:
>>>>         
>>>>> It would be nice if it did let you read/write to the same storage if it
>>>>> were possible - as it is in my case, as I am exclusively using
>>>>> disk-based storage.
>>>>>           
>>>> Unfortunately it is not possible to read and write to the same device,
>>>> because on a tape it is just impossible, and on a disk, it requires two
>>>> I/O packets.
>>>>
>>>> The above said, it is possible to read and write to the same disk
>>>> directory providing the volumes are different.  This is most easily
>>>> accomplished by using something such as the virtual disk changer
>>>> (disk-changer script), which provides two or more virtual drives.  It is
>>>> probably also possible by using the virtual disk device, which is a sort
>>>> of automatic disk changer, but I don't use that code, so I hesitate to
>>>> recommend it.
>>>>         
>>> I've been trying to get the disk-changer script to work for me, looking at
>>> the virtual backup regression tests for clues.
>>>
>>> Unless I'm wrong, it seems that you can't just schedule jobs and let it get
>>> on with it, filling up the slots with data and switching between them, as
>>> you have to manually enter commands to load, unload and label the slots.
>>>       
>> No, it is totally automatic.
>>     
>
> Sorry, I don't believe that this is correct, and here are some reasons:
>
> If, for example, I comment out these lines in tests/virtual-backup-test...
>
> label storage=File volume=FileVolume001 Pool=Default
> label storage=DiskChanger volume=ChangerVolume001 slot=1 Pool=Full drive=0
> label storage=DiskChanger volume=ChangerVolume002 slot=2 Pool=Full drive=0
>
> ...then the test seems to get stuck when it tries to run the first job. I
> connect to the director and it gives me the following message:
>   

Tapes (or disk-based volume files in this case) still have to be 
labeled. However, the labeling is automated using a tape device's 
barcode reader, (or emulation thereof), using the "label barcodes" 
Bacula console command. See 
http://www.bacula.org/en/rel-manual/Autochanger_Resource1.html#SECTION0032110000000000000000

> 20-Oct 10:36 localhost-dir JobId 1: Start Backup JobId 1, Job=Vbackup.2008-10-20_10.36.03
> 20-Oct 10:36 localhost-dir JobId 1: Using Device "FileStorage"
> 20-Oct 10:36 localhost-sd JobId 1: Job Vbackup.2008-10-20_10.36.03 waiting. Cannot find any appendable volumes.
> Please use the "label"  command to create a new Volume for:
>     Storage:      "FileStorage" (/usr/bin/bacula/regress/tmp)
>     Pool:         Default
>     Media type:   File
>
>
> Secondly, there is this comment in the top of the disk-changer script:
> # The Volumes will be created with names slot1, slot2, slot3, ... maxslot in the
> #  base directory.
>
> But the virtual backup-test runs scripts/prepare-disk-changer at the beginning,
> which does the following:
> #!/bin/sh
> #
> # Create fresh virtual disk changer directory
> #
> rm -rf tmp/disk-changer
> mkdir tmp/disk-changer
> # Create 10 slots
> for i in 1 2 3 4 5 6 7 8 9 10 ; do
>    touch tmp/disk-changer/slot$i
> done
>
> So, either the comment in the disk-changer script is wrong, or
> prepare-disk-changer is unnecessary.
>
>
> Thirdly, when I set up my bacula to use the disk-changer script, and run a
> job, I get a comment in my log that looks similar to this section in the
> 'kernstodo' file in svn:
>
> - Auto update of slot:
>    rufus-dir: ua_run.c:456-10 JobId=10 NewJobId=10 using pool Full priority=10
>    02-Nov 12:58 rufus-dir JobId 10: Start Backup JobId 10, Job=kernsave.2007-11-02_12.58.03
>    02-Nov 12:58 rufus-dir JobId 10: Using Device "DDS-4"
>    02-Nov 12:58 rufus-sd JobId 10: Invalid slot=0 defined in catalog for Volume "Vol001" on "DDS-4" (/dev/nst0). Manual load my be required.
>    02-Nov 12:58 rufus-sd JobId 10: 3301 Issuing autochanger "loaded? drive 0" command.
>
> (after this point, my messages diverge with different problems - I can send
> them to the list later)
>
>
>   
>>> I've also tried to find out what you mean by 'the virtual disk device', but
>>> I'm not able to find anything. Is there any documentation about this
>>> anywhere?
>>>       
>> At the top of the disk-changer script.
>>     
>
> I think you misunderstood me. Here is your original comment again:
>
>   
>>>> The above said, it is possible to read and write to the same disk
>>>> directory providing the volumes are different.  This is most easily
>>>> accomplished by using something such as the virtual disk changer
>>>> (disk-changer script), which provides two or more virtual drives.
>>>>         
> ...
>   
>>>> It is probably also possible by using the virtual disk device, which is
>>>> a sort of automatic disk changer, but I don't use that code, so I
>>>> hesitate to recommend it.
>>>>         
>
> You appear to be talking about two different things here. Firstly, the
> 'virtual disk changer (disk-changer script)', and secondly, the 'virtual disk
> device'.
>
> As I am having trouble getting the disk-changer script to work for me, I
> thought that the alternative 'virtual disk device' that you mentioned could
> be worth trying. There is no mention of such a thing at the top of the
> disk-changer script. So what is the 'virtual disk device'?
>
> Thanks for any help,
> Graham.
>
>
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