[CentOS] slow usb hard disk performance.

Tue Dec 6 22:39:46 UTC 2005
Matt Hyclak <hyclak at math.ohiou.edu>

On Tue, Dec 06, 2005 at 12:07:42PM -0600, Les Mikesell enlightened us:
> > > Amanda uses dump or tar for the backups and adds one extra block
> > > as a header to each backup.  You can strip off the header with
> > > dd and restore with dump or tar alone.  It was a nice system
> > > 15 years ago but hasn't had a lot of development since.  It
> > > has one big flaw in that it can't split a single filesytem
> > > backup across more than one tape even though it can do many
> > > hosts/filesystems in one run splitting different backups within
> > > the run over different tapes. With todays big disks that's probably
> > > fatal.
> > 
> > I hardly consider it fatal.  I backup 5.5TB of space (4 FSs) to
> > an AIT3 changer without a problem.  Also, tape spanning is included
> > in the 2.5 branch, which is officially in beta now.
> 
> The really brilliant part of amanda is the way it schedules the
> mix of full and incremental runs each night to fill a tape of
> a given size.  This works nicely when you have a large number
> of small filesystems (relative to the tape size) but falls down
> badly when a single full nearly fills the tape because it will
> start streaming some small runs that are finished first, then
> the big one won't fit, and even during amflushes it doesn't
> know enough to put the big run on the tape first so you end up
> with the small ones that can be grouped in a later amflush. The
> tape spanning change may help a lot with this.

You can also adjust the dumporder parameter to coerce amanda into doing all
the biggest dumps first, or the longest dumps to complete, etc. etc.

-- 
Matt Hyclak
Department of Mathematics 
Department of Social Work
Ohio University
(740) 593-1263