Jon LaBadie wrote: > On Mon, Aug 07, 2006 at 02:37:17PM -0400, Ian Turner wrote: >> Marilyn, >> >> Amanda's tape selection policy is as follows. >> >> Consider the set of tapes T. We can partition the set into two disjoint >> subsets A (the set of active tapes) and I (the set of inactive tapes). >> Assuming I is nonempty, there exists a subset P of I, called the set of >> preferred tapes. Note that T = A + I, and P is a weak subset of I. >> >> Amanda will only use tapes from I; active tapes are not considered for >> overwriting. Also, tapes from P are preferred to other tapes in I; a tape >> not >> in P (but in I) will be used only if no tapes in P are available. If no >> tapes >> from I are available, then no tapes are used and Amanda will go into >> degraded >> mode. >> >> Tapes are assigned to each of the two sets as follows: >> -- Any labeled but unused tapes are in I and P. This includes unlabeled >> tapes >> if the label_new_tapes option is set. >> -- The most recently used "tapecycle" number of tapes is in A. >> -- Any remaining tapes are in I. The single least recently used of these is >> also in P. >> >> This algorithm is applied from scratch any time a new tape is needed during >> a >> backup run. You can run the algorithm without running Amanda by doing >> 'amtape >> taper'. >> >> What all of this means from a slightly less mathematical perspective is that >> Amanda will not consider overwriting the tapecycle most recent tapes. If you >> want to relax this restruction, just reduce tapecycle, and Amanda will >> countenance the use of newer (more recently used) tapes. >> >> Alternatively, if you have a specific tape that you want Amanda to reuse, >> just >> relabel it, and it will be treated as a new tape. >> >> --Ian >> >> On Monday 07 August 2006 13:10, HUGHES Marilyn F wrote: >>> We have a situation where the next Amanda tapes that it is asking for >>> are currently offsite. It costs $75 for them to be retrieved so we >>> don't want to do that. >>> >>> >>> Besides we have available tapes here onsite. Is there a way (a command >>> or other way?) to force Amanda to select one of the tapes that we have >>> onsite? Does Amanda select from the top of the tapelist on down? > > > Ian, > > Thanks for your description. I was thinking of trying to put together > a description of the tape selection algorithm myself. But I didn't > know some(most?) of the detail. Certainly not in mathematical sets. > > One thing still up in the air (to me anyway) is final tape selection > from within the tapelist and physical tape changer. Your description > gets to which tapes are "eligible" to be selected, but not which tape > (or runtape number of tapes) among that set is ultimately chosen. > > Let me try to use my own terminology to descibe your algorithm so > that I'm sure I understand it. I'd appreciate corrections to any > mis-statements, in fact or in timing. And, perhaps you could extend > it by describing the final tape selection. > > From the entire tapelist, those marked "no-reuse" are eliminated > from further consideration. Only those marked "reuse" are considered. > (is there any other tapelist classification?) > > The reuse"able" list is divided into "previously used" and "never used" > (have a valid date stamp or have a 0 date stamp respectively). > > The previously used tapes are date-sorted and the most recently used > tapecycle-1 of those are eliminated from further consideration. This > would be your "active" set that are reusable but can't be overwritten > at this time as they fall within a tapecycle's number of tapes. > > Any remaining, previously used tapes, plus the labeled but never used > tapes (if any), constitute the set of tapes eligible to be used for > the next run. > > If what I've described is reasonably accurate, none of it is dependent > on tapelist order nor availability in the tape changer. So the physical > device must be accessed before the final selection of a tape to use. > > Does amanda at this point look specifically for the next tape based on > the order in the tapelist file? (i.e. the last tape in the tapelist > file that is on the eligible list) Will it scan the entire changer > looking for that specific tape? Or will it start to scan the changer > looking for any tape from the eligible list? Or something else? > > Thanks. > > jl If Amanda's behavior hasn't changed (I'm still using 2.4.5), it will use the first non-active tape it finds in the changer. It appears to just load the next tape until it finds a non-active one, not look for an unused one or find the oldest.
Frank -- Frank Smith [EMAIL PROTECTED] Sr. Systems Administrator Voice: 512-374-4673 Hoover's Online Fax: 512-374-4501
