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Re: [Bacula-users] When does bacula use multiple tape drives
2014-03-31 13:41:51
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On 3/31/2014 12:04 PM, Randall Svancara
wrote:
Hi,
Looks like I can use both drives when I add
Changer Device = /dev/changer-sg2
to
the bacuala-sd.conf file
and
additionally I had to add to the Storage directive
Device = Qualstar
Yes, it is a little confusing. A 2-drive autochanger is really 3
physical devices and usually has 3 SCSI LUNs, one for each actual
tape drive and one for the robot that moves tapes in and out of the
tape drives. Bacula handles this with the Autochanger resource
defined in bacula-sd.conf which serves two purposes. One is to
define the SCSI LUN and script used to send commands to the tape
robot. The other is to determine which Device resources are the
autochanger's actual tape drives, or in other words the list of
Device resources that Bacula may assign to jobs that are
reading/writing to the Autochanger resource.
The actual tape drives in the autoloader are handled like any other
tape drive with a Device resource definition in bacula-sd.conf. Thus
the individual drives belonging to a multi-drive autoloader can be
used as a stand-alone tape drive, if so desired, by specifying the
SD's Device resource in the DIR's Storage resource. This is useful
if there is a specific job that you want to dedicate a drive to.
Perhaps there is a high priority job that is time constrained and
must never have to wait on an available drive. In the normal use
scenario, you specify the SD's Autochanger resource in the DIR's
Storage resource, meaning that you want Bacula to select the first
available drive and it doesn't matter which one gets selected.
# Definition of LTO tape storage device
Storage {
Name = "Qualstar"
#Do not use "localhost" here
Address = localhost # N.B. Use a fully
qualified name here
SDPort = 9103
Password = "haaaaahahahahahahahaahah" #
password for Storage daemon
#Device = Drive-1 # must be same as
Device in Storage daemon
#Device = Drive-2
Device = Qualstar
Media Type = LTO6 # must be same as
MediaType in Storage daemon
Autochanger = yes # enable for
autochanger device
Maximum Concurrent Jobs = 2
}
In the bacula-dir.conf.
Apparently you have to reference the changer, not the
actual tape devices like this example below.
Device = Drive-1
# must be same as Device in Storage daemon
Device = Drive-2
I don't know what happens when two Device lines appear in the
Storage resource. I suspect only one is used.
In
terms of running multiple jobs, and writing to the same
tape...this sounds like a pretty cool idea that Bacula can
interleave the jobs. How long has it been able to do this.
When I first used this software many years ago, it did not
seem like this was available or maybe it was not advocated
for reasons mentioned before.
The only con with interleaving that I'm aware of is that it can make
restores slow because it basically has to read all of the
interleaved job data in order to restore one job.
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