On Tue, Nov 30, 2004 at 01:24:49PM -0500, Brian Cuttler wrote:
> On Tue, Nov 30, 2004 at 06:10:22PM +0100, Stefan G. Weichinger wrote:
> > [suggests "taperalgo"]
> 
> There is a dumporder parameter in amanda.conf [...]
> 
> I do not know if dumporder is utilized when scheduling the clients or
> when scheduling taper.

For dumps that use a holding disk, dumporder is used when
scheduling which DLE to dump next.  There are several "dumper"
processes running on the Amanda server ("inparallel" of them, I
believe); they interface with the clients, receive the dump data,
and either write it to holding disk or pipe it to the (single)
"taper" process.  Each dumper process can handle multiple DLEs
*serially*, but only one at a time.

When a dumper is ready to start processing another DLE, the
"driver" process assigns it one.  Driver looks at which of the
remaining DLEs are potentially dumpable at the moment (given
constraints such as available holding disk space, network
bandwidth, etc.).  From that subset, it chooses one based on some
priority ordering.

That ordering comes from "dumporder".  At startup, each dumper
process is assigned a priority ordering from one of the letter
codes, and continues to use the same ordering for the duration of
the run.

When the taper process is ready to start taping another DLE,
again driver assigns it one, from among the DLEs on holding disk
that have already completed dumping (Amanda does *not* pipeline
dumping a given DLE to holding disk, and from there to tape).
"taperalgo" determines which of the completed DLEs to tape next.

For dumps direct to tape (i.e. bypassing the holding disk), it
looks as though those aren't even attempted until all the dumps
that *do* use the holding disk have finished (i.e. are on tape).
Then, neither dumporder nor taperalgo are used; the remainining
DLEs are processed (one at a time of course) in their order in
the queue, which in turn is the order that the "planner" process
chose, based on a whole other set of criteria...

--

|  | /\
|-_|/  >   Eric Siegerman, Toronto, Ont.        erics AT telepres DOT com
|  |  /
The animal that coils in a circle is the serpent; that's why so
many cults and myths of the serpent exist, because it's hard to
represent the return of the sun by the coiling of a hippopotamus.
        - Umberto Eco, "Foucault's Pendulum"