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Re: [Bacula-devel] concurrent multidrive use


Hello,

After having discussed this a bit on the list, and re-reading your note here, 
I realize that yes splitting to separate tapes would be possible on a file by 
file basis.  However, that feature would work much better if the multiple 
threads for a given job were implemented, which is already a project listed 
in the Projects file.

Regards,

Kern


On Monday 21 July 2008 19:55:20 T. Horsnell wrote:
> OK, thanks. And sorry to have pestered the development *and* the users
> list about this. I just wanted to be sure you understood what I meant.
>
> Actually, I would have said that striping was the process of spreading a
> single *file* across multiple drives simultaneously (just like
> disk-striping). To my mind, spreading the files of a single *job* across
> multiple drives doesnt mean that part of each *file* is written to
> multiple drives, but instead, that when the storage daemon is writing to
> a device which has been declared as an autochanger with multiple drives,
> it would take the next file from its input stream and write it to an
> idle drive in that autochanger.
>
> I guess if the storage-daemon scheme has one thread per tapedrive,
> it doesnt lend itself to this mode of operation.
>
> THanks again,
> Terry
>
> Kern Sibbald wrote:
> > Yes, sorry, I did not understand.  Bacula does not have the ability to
> > write a single job to multiple drives -- normally that is called
> > striping.  It is unlikely that it will be implemented any time in the
> > near future.
> >
> > On Monday 21 July 2008 18:27:43 T. Horsnell wrote:
> >>Thank you for that quick reply, and once again, apologies for the
> >>interruption, but I dont want to split the backup across multiple jobs,
> >>(with part of the filesystem being handled by one job and part by the
> >>other), because however I make the split, the content (and hence the
> >>size) of each part of the filesystem will be continually changing (this
> >>is a 16TB multiuser raid system), and so one tapedrive may well be
> >>mostly idle whilst the other one is continually busy. So I want, if
> >>possible, to do this with a single job.
> >>
> >>Cheers,
> >>Terry
> >>
> >>Kern Sibbald wrote:
> >>>Hello,
> >>>
> >>>We generally do not supply support help on this list, but I will give a
> >>>few tips ...
> >>>
> >>>Bacula has been able to write to multiple drives simultaneously for a
> >>>very long time now -- many years and many versions.
> >>>
> >>>The simplest way to do it is to use different pools for each job.
> >>>
> >>>A not so satisfactory way of doing it is to use "Prefer Mounted Volumes
> >>> = no". I don't recommend this as it leads to many operational problems.
> >>>
> >>>In general, if you are backing up raid disks, you should be able to tune
> >>>your hardware so that it will write approximately 150 MB/sec with Bacula
> >>>to an LTO3 drive, and so splitting jobs is not generally necessary.
> >>>Getting your hardware tuned to run at those speeds is not easy and
> >>>requires professional help.
> >>>
> >>>Best regards,
> >>>
> >>>Kern
> >>>
> >>>On Monday 21 July 2008 17:20:11 T. Horsnell wrote:
> >>>>Apologies for pestering the developers list, but I cant determine from
> >>>>the user docs whether what I want to do is failing because I'm doing it
> >>>>wrongly, or simply that its not supported.
> >>>>
> >>>>I want to define a single job which will backup a single (big) raid
> >>>>filesystem to an autochanger which contains multiple tapedrives, and I
> >>>>want this job to use all the tapedrives simultaneously. This would seem
> >>>>to me to be a pretty standard requirement, but I cant get it to work
> >>>>with Bacula version 2.4.1
> >>>>
> >>>>Looking at the Storage Daemon section (6.4) in the new delvelopers docs
> >>>>for 2.5.2 (dated 20th July 2008 !) I see that this may not yet be
> >>>>possible:
> >>>>
> >>>>
> >>>>---cut---
> >>>>Today three jobs (threads), two physical devices each job writes to
> >>>> only one device:
> >>>>Job1 -> DCR1 -> DEVICE1
> >>>>Job2 -> DCR2 -> DEVICE1
> >>>>Job3 -> DCR3 -> DEVICE2
> >>>>
> >>>>To be implemented three jobs, three physical devices, but job1 is
> >>>>writing simultaneously to three devices:
> >>>>
> >>>>Job1 -> DCR1 -> DEVICE1
> >>>>        -> DCR4 -> DEVICE2
> >>>>        -> DCR5 -> DEVICE3
> >>>>Job2 -> DCR2 -> DEVICE1
> >>>>Job3 -> DCR3 -> DEVICE2
> >>>>---cut---
> >>>>
> >>>>Is what I want possible in 2.5.2, or should I wait?
> >>>>
> >>>>Cheers,
> >>>>Terry.
> >>>>
> >>>>
> >>>>
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