How To:Write to Multiple Volumes in Parallel

Amanda can write to multiple volumes in parallel, saving a lot of time.

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

• A Changer with the new changer API must be used.
• More than one drive must be defined.

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(5):

taper-parallel-write 2

Changer Configuration

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.

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"

See also

amanda.conf(5),amanda-changers(7)