Backup Central

Hi everybody,

We have been using Bacula 5.0.3 for a while with a setup that includes
one tape library with one LTO3 device.

We have upgraded to a new autochanger with two LTO4 devices. I'm hoping
to make maximum use of the second drive. But I have a question
regarding speed.

Here is our backup schedule:

---snip---

# When to do the backups, full backup on first sunday of the month,
# differential (i.e. incremental since full) every other sunday,
# and incremental backups other days
Schedule {
Name = "MonthlyCycle"
Run = Full 1st sun at 23:05
Run = Differential 2nd-5th sun at 23:05
Run = Incremental mon-sat at 23:05
}

--end snip--

I currently have Bacula correctly working with both devices. I have set
"Prefer Mounted Volumes = no" and Bacula is now maximizing the use of
the two devices when possible.

But will this speed up my backups? Generally speaking, should Bacula be
able to write two the two tapes devices more quickly than it can write
to one? The unit in question is a Tandberg Data StorageLibrary T24 LTO
with two serial attached scsi LTO4 tape devices, attached to a server
running Centos 6.2.

Is my arrangement the best way to maximize two tape drives?

Thanks for your input,
Bryan






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But will this speed up my backups?   Generally speaking, should Bacula be
able to write two the two tapes devices more quickly than it can write
to one?  The unit in question is a Tandberg Data StorageLibrary T24 LTO
with two serial attached scsi LTO4 tape devices, attached to a server
running Centos 6.2.

It will not speed up a single job since 1 job can not use more than 1
drive however if you have concurrent jobs with spooling and you can
provide enough bandwidth to keep up with the drives it can speed up
multiple jobs. Remember that at 2:1 compression these LTO4 drives
write at 120MB /s each so you will need to have a raid array (raid 0
maybe) or fast SSD for your spool location and this raid probably
should not be on the same drives as your source data.

John

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Thanks for the reply, John. I'll give it a go. The spooling will be on
RAID 10, so I won't get the performance of RAID 0, but we will see how
it goes.

Cheers,
Bryan

On Mon, 2012-01-23 at 17:59 -0500, John Drescher wrote:
But will this speed up my backups? Generally speaking, should Bacula be
able to write two the two tapes devices more quickly than it can write
to one? The unit in question is a Tandberg Data StorageLibrary T24 LTO
with two serial attached scsi LTO4 tape devices, attached to a server
running Centos 6.2.

It will not speed up a single job since 1 job can not use more than 1
drive however if you have concurrent jobs with spooling and you can
provide enough bandwidth to keep up with the drives it can speed up
multiple jobs. Remember that at 2:1 compression these LTO4 drives
write at 120MB /s each so you will need to have a raid array (raid 0
maybe) or fast SSD for your spool location and this raid probably
should not be on the same drives as your source data.

John



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