dump(8) performance

[Dirk Engling]

On Wed, 31 May 2006, Eugene M. Kim wrote:

> read throughput was exactly twice as high as the tape write throughput,
> throughout the entire dump phases 4 and 5, i.e. dumping actual inodes.
> Disappointing, because the tape drive utilization (%busy) was lingering
> around 35%-50% for most of the time; I didn't expect the disk would be
> the bottleneck. :p

I had a similar experience when dumping my mailserver. In addition I 
noticed that for a user with >300000 files (spam mails) in one directory 
it caused dump to sit back and think for half an hour before proceeding.

I always resolved to look into the code to find something O(x^n) but 
didn't have the real urge. DID someone here look into that?

Regards

   erdgeist