On 01/27/11 10:48, Graham Keeling wrote:
> The same problems exist in more realistic situations.
> 
> Assuming that I somehow know that all my backups will range from 100MB to 
> 10GB,
> then what should I set?
> 
> a) 10000 volumes, 100MB max size?
> b)   100 volumes,  10GB max size?
> 
> a) gives me wasted space when a backup is not a multiple of 100MB in size,
> and possible overhead problems due to the number of volumes.
> b) gives me wasted space when a backup is not a multiple of 10GB in size.

If you insist on limiting your number of volumes to the number of
maximum-size volumes that would fill your disk and restricting the
number of jobs allowed on a volume, yes, one could argue that it does.
But any time your Bacula pool design answer involves "Max Volume Jobs =
1", the probability is extremely high that you started out by asking the
wrong question.

The problem here is not that the directives don't work, or that any
particular method of governing volume size wastes space.  It's that ANY
possible set of volume management options is capable of being misused to
create pathological configurations that waste disk space.  If you only
allow yourself 100 volumes on a 1TB disk, and then write 1GB to each one
and complain that the remaining 900GB of disk space is "wasted" because
you can't create any more volumes and can't append to any of the ones
you have, you only have yourself to blame; you consciously, with malice
aforethought, took careful aim and shot yourself in the foot with an
elephant gun.


-- 
  Phil Stracchino, CDK#2     DoD#299792458     ICBM: 43.5607, -71.355
  alaric AT caerllewys DOT net   alaric AT metrocast DOT net   phil AT 
co.ordinate DOT org
         Renaissance Man, Unix ronin, Perl hacker, Free Stater
                 It's not the years, it's the mileage.

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