> -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] > On Behalf Of Jon LaBadie > Sent: Tuesday, August 08, 2006 2:32 PM > To: [email protected] > Subject: Re: Next Tapes are Offsite > > > On Tue, Aug 08, 2006 at 10:27:00AM -0500, Frank Smith wrote: > > 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. > > > > From this discussion, your and my observations also, it appears the > order of tapes listed in the tapelist file is immaterial. > > Anyone disagree? [McGraw, Robert P.] Not from what I see. I always reverse sort my tape list so that the oldest and lowest number is at the bottom.
zorn->[537] > cat tapelist
0 D00010 reuse
0 D00009 reuse
0 D00008 reuse
0 D00007 reuse
0 D00006 reuse
0 D00005 reuse
0 D00004 reuse
0 D00003 reuse
0 D00002 reuse
0 D00001 reuse
zorn->[538] > amadmin daily tape
The next Amanda run should go onto a new tape.
a new tape.
The next 2 new tapes already labelled are: D00001, D00002.
zorn->[541] > cat tapelist
0 D00001 reuse
0 D00002 reuse
0 D00003 reuse
0 D00004 reuse
0 D00005 reuse
0 D00006 reuse
0 D00007 reuse
0 D00008 reuse
0 D00009 reuse
0 D00010 reuse
zorn->[539] > amadmin daily tape
The next Amanda run should go onto a new tape.
a new tape.
The next 2 new tapes already labelled are: D00010, D00009.
Robert
>
> --
> Jon H. LaBadie [EMAIL PROTECTED]
> JG Computing
> 4455 Province Line Road (609) 252-0159
> Princeton, NJ 08540-4322 (609) 683-7220 (fax)
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