Bumped to amanda-users since no response on amanda-hackers.
On 2/15/07, Terry Burton <[EMAIL PROTECTED]> wrote:
Hi, I wouldn't like to guarantee that I have completely understood the intended tape selection algorithm so please correct me if this suggestion does not make sense. I am running a multi-tape random access tape changer with a barcode scanner. My tapelist contains a number of entries that at least for the moment contain an ordered sequence of labels, some of which have been used for backup (date != 0) and others are new (date == 0). After a dump/flush, amadmin.c reports "The next %d new tapes already labelled are: %s"... which successfully picks the next few tapes from the bottom of the tapelist using lasttp = lookup_tapepos(lookup_nb_tape()). This is a sensible selection of tapes based on the current tapelist. However, the amtape_taper_scan function of amtape.c invokes lookup_last_reusable_tape(0) which will in this case return NULL to signify that any new tape is required. Hence, amtape Daily taper will settle on whatever new tape is in or ahead of the current slot, rather make the better choice of the "next tape already labelled" (as derived in amadmin.c). Consequently, in order to maintain our labeling scheme (necessary since the tape are collected from offsite), our backup operators have to load the tapes in ascending label order and perform amtape Daily reset/first to reset the current slot, or alternatively they could load the tape in ascending order from the position of the current slot without running invoking amtape. I suggest making it an option to (possibly) trade in fast tape selection for the sake of more intelligent tape selection so that when this option is enabled amtape Daily taper should first attempt to select the "next tape already labelled" (tapelist-based) and if this tape is not available then fall back to "the any new tape" (slot-based) algorithm, assuming of course you have a random access changer with a barcode unit. In the case that the changer is inventory aware (via a barcode scanner), there would be no performance penalty and this could become the default selection algorithm. The benefit would be that people running random access, inventory aware changers would be able to load their tapes in random slots and change tapes without resorting to the amtape utility. I look forward to hearing if this is possible. Many thanks, Tez
