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NBU Trick #2 - Slow Filling; More Tape? |
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Written by Paul Winkeler
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Monday, 28 April 2003 |
The corollary to NBU Trick #1, "Where Did All My Tapes Go?" is the question "How Long Does it Take to Fill a Tape?". The trick to answering this question is to make use of three tape attributes NetBackup kindly tracks for us:
The date on which the tape was allocated to the media server. The assumption being made that this is then also the date on which the tape was first written.
The date on which the tape was last written.
And of course the bit that tells us the tape is in fact full
The snippet of NBU empowered code you need to compute this interval then trivially becomes:
print "Volume ".$volume->id." took ".$volume->fillTime." seconds to fill\n";
Of course this is cheating and it only works because NBU's Media objects happen to have a fillTime() method. The attributes we alluded to above are in fact used in this method's implementation reproduced here:
sub fillTime {
my $self = shift;
return $self->full ? ($self->{LASTWRITTEN} - $self->{ALLOCATED}) : undef;
}
Do be careful because as you can see, asking for the fillTime() of a tape not yet empty, gives and undefined result!
With this bit of information in hand, it is possible to compute the average amount of time it takes to fill a tape. Group that statistic by retention level and volume pool and you should get a pretty good idea of the speed with which your tapes are consumed. |
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Last Updated ( Friday, 21 September 2007 )
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