On Mon, Aug 11, 2003 at 12:01:22PM -0400, Brian Cuttler wrote: > Largestfit() isn't some balancing act between the estimate size > and the capacity of the spool/holding area ?
No, it's not that smart. > What is the algorithm for starting the dumps anyway ? Here's the pseudocode (from driver.c:startaflush()): dp = NULL; switch (conf_taperalgo) { ... case LARGESTFIT: dp = find_largest_dump_that_fits(); break; } if (dp == NULL) dp = first_dump(); In other words, if the user's chosen taper algorithm can't find any dumps it likes, Amanda just goes with the first tape-ready dump on its list, regardless of whether there's enough tape to hold it. I suppose it's trying to keep the tape drive busy, and crossing its fingers that the first dump will fit anyway (e.g. if the tapetype underestimates the tape length). But if the first dump doesn't fit, both the rest of the tape in question, and the time to write it, have been wasted. I can think of a few things it could do that might be better than picking the first dump in its list: 1. Choose the *smallest* dump that's ready for taping -- if any "too-large" dump is going to fit, that's the one. This might only make sense for FIRSTFIT and LARGESTFIT; the other algo's don't care whether the chosen dump is going to fit, so if they haven't found any they like, there's a different reason for it. 2. Just eject the tape immediately, and go on to the next one; the space will still have been wasted, but not all that writing time. Maybe this only makes sense if we know that this run has more tapes available; if we're on the run's final tape, a last-ditch effort to fill it up doesn't cost anything. 3. As Orion suggested, wait for more dumps to become available, in the hope that one will be small enough. It might make sense to keep waiting, if necessary, until all dumps have finished, but that risks filling the holding disk, so perhaps it should only wait for a limited time, or until the holding disk fills to some threshold. Better still, this decision should be user-configurable. This was discussed in amanda-users a few months ago. The thread starts here: http://groups.yahoo.com/group/amanda-users/message/43375 I had some ideas then; at the risk of tooting my own horn a bit, here are pointers to them, for people reading amanda-hackers who don't also read amanda-user (stupid yahoogroups trashed the indentation): http://groups.yahoo.com/group/amanda-users/message/43429 http://groups.yahoo.com/group/amanda-users/message/43437 -- | | /\ |-_|/ > Eric Siegerman, Toronto, Ont. [EMAIL PROTECTED] | | / When I came back around from the dark side, there in front of me would be the landing area where the crew was, and the Earth, all in the view of my window. I couldn't help but think that there in front of me was all of humanity, except me. - Michael Collins, Apollo 11 Command Module Pilot