How To:Write to Multiple Volumes in Parallel: Difference between revisions

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Amanda can write to multiple volumes in parallel, saving a lot of time.
Amanda supports [[Parallel Writes to Tape|parallel writes to tape]], meaning that the Amanda server can send multiple DLEs to different volumes at the same time. This is useful if you write to more than one volume in a run and the changer have more than one drive.
 
This is useful if you write to more than one volume in a run and the changer have more than one drive.
 
* A different dle is sent to each volumes.
* All parts of a dle are contiguous on a volume.
* If splitting is enabled and a volume get EOT, the next part of the dle can be on any volume, not necessarily on a new volume.
* The use of holding disk is still recommended, it allow more dumps in parallel and many dles are not fast enough to stream a tape drive.
* If a drive is not available at the beginning of the run, amanda will not use it, it doesn't poll for available drive.
 
= Advantage =
* Writing to many volume in parallel save times.
* Can do more than one dump direct to tape in parallel.
 
= Disadvantage =
* Require a more powerful server to be able to stream multiple drives.
* Performance can be worse if the server can't stream all the drives.


= Requirements =
= Requirements =
* A Changer with the new changer API must be used.
* A changer with the new [[changer API]] must be used.
* More than one drive must be defined.
* The changer must provide more than one drive
 
= Global Configuration =
The '''taper-parallel-write''' config option must be set to the number of volume amanda can write to in parallel.
 
In amanda.conf:
taper-parallel-write 2
 
= Changer Configuration =
How to defined multiple drives:
How to defined multiple drives:
* chg-disk: Nothing to do, an infinite number of drive is already available.
* chg-disk: Nothing to do, an infinite number of drive is already available.
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* chg-robot: Define all drives with the '''tape-device''' property.
* chg-robot: Define all drives with the '''tape-device''' property.
* chg-single: Impossible to do, only one drive is available.
* chg-single: Impossible to do, only one drive is available.
= Configuration =
Only one {{man|5|amanda.conf}} parameter affects parallel writes:
taper-parallel-write 2
the number gives the maximum number of parallel writes that are allowed.


= Examples =
= Examples =
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  taper-parallel-write 2
  taper-parallel-write 2
  tpchanger "chg-disk:/path/to/vtapes"
  tpchanger "chg-disk:/path/to/vtapes"
* chg-robot
* chg-robot
  taper-parallel-write 2
  taper-parallel-write 2
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  }
  }
  tpchanger "hp-robot"
  tpchanger "hp-robot"
Note that, for the chg-robot configuration, the <tt>taper-parallel-write</tt> parameter must be less than or equal to the number of drives configured with the TAPE-DEVICE property.


= See also =
= See also =


{{man|5|amanda.conf}},{{man|7|amanda-changers}}
* [[Parallel Writes to Tape]]
* {{man|5|amanda.conf}}
* {{man|7|amanda-changers}}

Revision as of 23:20, 28 September 2010

Amanda supports parallel writes to tape, meaning that the Amanda server can send multiple DLEs to different volumes at the same time. This is useful if you write to more than one volume in a run and the changer have more than one drive.

Requirements

  • A changer with the new changer API must be used.
  • The changer must provide more than one drive

How to defined multiple drives:

  • chg-disk: Nothing to do, an infinite number of drive is already available.
  • chg-multi: Nothing to do, all drives are already defined.
  • chg-ndmp: Define all drives with the tape-device property.
  • chg-robot: Define all drives with the tape-device property.
  • chg-single: Impossible to do, only one drive is available.

Configuration

Only one amanda.conf(5) parameter affects parallel writes: 

taper-parallel-write 2

the number gives the maximum number of parallel writes that are allowed.

Examples

  • chg-disk
taper-parallel-write 2
tpchanger "chg-disk:/path/to/vtapes"
  • chg-robot
taper-parallel-write 2
define changer hp-robot {
    tapedev "chg-robot:/dev/sg1"
    property "tape-device" "0=tape:/dev/nst0"
    property append "tape-device" "1=tape:/dev/nst1"
}
tpchanger "hp-robot"

Note that, for the chg-robot configuration, the taper-parallel-write parameter must be less than or equal to the number of drives configured with the TAPE-DEVICE property.

See also

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