Hi List,

I believe that I have run into a problem in the way that the traditional
taper scan algorithm tries to detect that all tapes have been inspected
and would value any feedback or suggestions.

Our installation is from the Amanda 3.3.0 Debian package, configured to
use Taper::Scan::traditional and Changer::robot.

On this particular run, the content of our tape libray looked like this:

X ... X 1* 3 2* X

where X represents a non-reusable tape and 1,2,3 represent three reusable
tapes ordered from oldest to newest (but not residing in the library in
that order). Tapes marked with a * are barcode labeled (alas, not all of
them are).

What happens when all three reusable tapes are needed for a backup run is,
according to the taper debug log, that scan stage 1 finds tape 1, then
tape 2, then fails to find tape 3. That is as expected. Not scan stage 2
starts with the next slot after tape 2 and sequentially scans all tapes
up to tape 1, where the scan terminates and reports that "all slots have
been loaed". Which is wrong, tape 3 was never touched because stage 1
has skipped over it.

A little research showed that the condition for terminating scan stage 2
is (paraphrased) "inspecting a tape slot that has been inspected before",
which is quite all right if _only_ stage 2 is run because it leaves no
uninspected "holes" in the tape library. But when both stages are run this
can lead to unnecessarily failed taper runs.

So you say, put barcodes on all your tapes then. But scan stage 1 will
never return an unlabeled tape (according to the documentation). So
supposing we need three tapes out of an library stocked like this:

X ... X 1* U* U* 2* where U represents an unlabeled tape.

Again stage 1 will return tapes 1 and 2, then stage 2 will terminate
without suggesting any of the unlabeled tapes.

So am I right in thinking that this is a bug?

Regards,
Ralph

-- 
Ralph Rößner
CAPCom AG < http://www.capcom.de >
Lise - Meitner - Straße 10, 64293 Darmstadt, Deutschland
Phone +49 6151 155 910, Fax +49 6151 155 909
Mobil: +49 170 2212 411

Vorstand: Luc Neumann (Vorsitzender)
Vorsitzender des Aufsichtsrats: Herbert Kuhlmann
Sitz der Gesellschaft: Darmstadt, Registergericht: Darmstadt HRB 8090

Reply via email to