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List:       bacula-users
Subject:    Re: [Bacula-users] Multiplexing multiple jobs to tape
From:       "John Drescher" <drescherjm () gmail ! com>
Date:       2007-08-31 12:14:23
Message-ID: 387ee2020708310514y5f24c8bbu1ee1e21ff5e7f155 () mail ! gmail ! com
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>  Since tape is a linear medium, and not random-access, the only plausible
> way for what you suggest to work would be for Bacula to interleave data
> blocks from two or more backup jobs.
This is what spooling is for.

> At a minimum, this would require
> writing incredible amounts of data to the backend database to keep track of
> which blocks on a given tape belong to which portions of a given file from a
> given backup.
>
>  I very much doubt Bacula can do anything quite like that.
>
Spooling  and machine separation (I mean the director, storage and
database are on different multi processor servers with 4GB or more of
RAM) takes care of that.
>
>  You should probably spend more time looking into your network instead.
>
The harder part is feeding 120 MB/s over the network to the bacula-sd.
This will require at least 2 gigabit NICs on the bacula-sd device and
you would need to somehow get your jobs to load balance the data to
the different NICs.


On top of that  the spooling area (on the bacula-sd) will have to be a
RAID (0,5,6) because no single drive will read and write
simultaneously at that rate.

John

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