On 2014-11-15 12:17, Brady, Mike wrote:
> First of all thanks to Kern and Bacula Systems for making the "Best
> Practices for Disk Based Backup" and "Disk Back Design" documents
> available.
> 
> I have been playing around with the best way for doing concurrent
> backups for a while and these documents have helped my understanding
> considerably.  Using a Virtual Autochanger in particular seems an
> elegant way of doing what I would like to do.
> 
> However, I am seeing some behaviour in my testing that I did not expect
> and I need some input.
> 
> At a high level what I am trying to do is use a Virtual Autochanger to
> write to multiple volumes in the same pool concurrently.
> 
> At the moment I have two devices limited to one concurrent job each.
> Which, if I have understood things correctly, means that I should have
> two jobs running concurrently writing to separate volumes.  The 
> schedule
> below kicks off eight jobs simultaneously with the number of devices
> limiting concurrency.
> 
> This issue that I am having is that the first job gets FileChgr1-Dev1
> and a volume as expected.
> 
> The second job gets device FileChgr1-Dev2 as expected, but always says
> "Cannot find any appendable volumes." and issues a mount request.  
> There
> are multiple purged volumes with the recycle flag set available in the
> IncPoool pool. Even if there weren't, the pool has Auto Labelling
> configured and has not reached the MaximumVolumes limit, so there 
> should
> "always" be a volume available.
> 
> Other jobs continue to use the FileChgr1-Dev1 as it becomes available
> while FileChgr1-Dev2 is waiting for a volume.
> 
> The second job eventually retries on FileChgr1-Dev2, gets an available
> volume and successfully completes without any operator intervention.
> 
> After this the remaining jobs utilise both FileChgr1-Dev1 and
> FileChgr1-Dev2 as they become available as I expected.
> 
> Is this behaviour expected (I am assuming some sort of race condition 
> at
> the start of the schedule with multiple jobs trying to get a volume at
> the same time) or am I trying to do something fundamentally wrong here?
> 
> My configuration is:
> 
> Pool {
>    Name = IncPool
>    Pool Type = Backup
>    Volume Use Duration = 23 hours
>    Recycle = yes
>    Action On Purge = Truncate
>    Auto Prune = yes
>    Maximum Volumes = 50
>    Volume Retention = 2 weeks
>    Storage = FileStorage01
>    Next Pool = "IncPoolCopy"
>    Label Format = "IncPool-"
> }
> 
> Storage {
>    Name = FileStorage01
>    Address = 192.168.42.45
>    SDPort = 9103
>    Password = ***************************
>    Device = FileChgr1
>    Media Type = File01
>    Maximum Concurrent Jobs = 10
>    Autochanger = yes
> }
> 
> Autochanger {
>    Name = FileChgr1
>    Device = FileChgr1-Dev1, FileChgr1-Dev2
>    Changer Command = /dev/null # For  7.0.0 and newer releases.
>    # Changer Command = "" # For 5.2 and older releases.
>    Changer Device = /dev/null
> }
> 
> Device {
>    Name = FileChgr1-Dev1
>    Drive Index = 0
>    Media Type = File01
>    Archive Device = /bacula_storage/FileDevice
>    LabelMedia = yes;
>    Random Access = Yes;
>    AutomaticMount = yes;
>    RemovableMedia = no;
>    AlwaysOpen = no;
>    Maximum Concurrent Jobs = 1
>    VolumePollInterval = 5s
>    Autochanger = yes
> }
> 
> Device {
>    Name = FileChgr1-Dev2
>    Drive Index = 1
>    MediaType = File01
>    ArchiveDevice = /bacula_storage/FileDevice
>    LabelMedia = yes;
>    RandomAccess = Yes;
>    AutomaticMount = yes;
>    RemovableMedia = no;
>    AlwaysOpen = no;
>    MaximumConcurrent Jobs = 1
>    VolumePollInterval = 5s
>    Autochanger = yes
> }
> 
> Schedule {
>    Name = "DefaultBackupCycle"
>    Run = Level=Full 1st sun at 00:10
>    Run = Level=Differential 2nd-5th sun at 00:10
>    Run = Level=Incremental mon-sat at 00:10
> }
> 
> Thanks
> 
> Mike
> 

I forgot to say I am running Centos 6.6 and Bacula 7.0.5.  Bacula 
packages are from 
http://repos.fedorapeople.org/repos/slaanesh/bacula7/epel-6/x86_64/

I also added a 3rd device just to see what would happen.  Not 
unexpectedly 2 mount request this time.  One each from the 2nd and 3rd 
jobs.

One difference this time was that there were no purged volumes available 
in the IncPool. This was on purpose.  The results were not good.  Three 
new volumes inserted into the DB, but only two created on disk.  This 
resulted in the third job being stuck trying to mount a non exist volume 
file.

I am obviously missing something quite fundamental here.

Regards

Mike

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