On Sun, Aug 29, 2010 at 11:10:40AM -0400, Dustin J. Mitchell wrote: > On Fri, Aug 27, 2010 at 2:41 PM, Chris Hoogendyk > <[email protected]> wrote: > > There was an exchange on the list in the last few months where I asked that > > question and Dustin replied. He said that the historical algorithm had a > > strong preference for an already written tape if one was available that > > could be written to. I think he said that now that the new taper was out he > > was thinking about implementing a more sane algorithm. > > Wow, I'm cited twice as historical precedent! > > If you look closely at amanda-taperscan(7), you'll see that the > unknown component of the algorithm that has changed in more recent > versions is whether the changer is fast-searchable. In the past, only > chg-zd-mtx+barcodes was searchable. Even chg-disk acted like a > barcode-less changer, and just scanned slots in order to find a tape. > > The traditional algorithm will "stumble across" new tapes with a > non-fast-searchable changer, but with a fast-searchable changer, it > will always search for the oldest reusable tape, paying no attention > to new tapes. > > It's unfortunate, but it's the way things have worked historically.
I've never worked with a barcoded changer so I never had a "fast-searchable" experience. You do not explicitly say so, but I assume chg-disk is now fast-searchable? That's not historical :) For my setup to reach all tapes used will take some time. Maybe you know the answer to this question. I've just experienced the skipping of new tapes to reuse just the tapecycle number of tapes. But how will the taperscan act if all the tapes have been used but tapecycle is less than the number of available tapes. As an example with numbers: suppose I have a 20 tape changer and fill it with labeled tapes. Then, with a tapecycle of 20 all tapes get used in order. Suppose I then reduce tapecycle to 15. Will the new tapescan algorithm skip 5 of the tapes and only use 15? -- Jon H. LaBadie [email protected] JG Computing 12027 Creekbend Drive (703) 787-0884 Reston, VA 20194 (703) 787-0922 (fax)
