We have found that a shorter dumpcycle simplifies restores.
We have also found that a shorter tape cycle simplified managerial
issues... We need to investigate XYZ user please bring back all copies
of their Lotus Notes mailbox.
We find 20-25 tapes ample for most situations, gives a month plus
restore period (we have dumps 5x/week) with a few of the older
amanda configs on sight having a shorter period (we have intranet
source for the external web server, we really only need to recover
the OS and that is current at least once per designated dumpcycle).
On Tue, Mar 15, 2005 at 01:03:31AM -0500, Jon LaBadie wrote:
> On Mon, Mar 14, 2005 at 09:14:43AM -0700, Tom Schutter wrote:
> > I had some questions regarding tapecycle, and after reading the man
> > page and the doc (old and new), I think that they fall short on
> > describing what tapecycle should be set to. The minimum value of
> > tapecycle is well covered, but not the maximum value, and how
> > tapecycle should relate to the number of tapes that have been
> > labeled.
> >
> > >From the man page:
> > tapecycle int
> > Default: 15 tapes. The number of tapes in the
>
> Gee, I did not realize there was a default :)
>
> > active tape cycle. This must be at least one
> > larger than the number of Amanda runs done during a
> > dump cycle (see the dumpcycle parameter) times the
> > number of tapes used per run (see the runtapes
> > parameter).
> >
> > For instance, if dumpcycle is set to 14 days, one
> > Amanda run is done every day (Sunday through Satur-
> > day), and runtapes is set to one, then tapecycle
> > must be at least 15 (14 days * one run/day * one
> > tape/run + one tape).
> >
> > In practice, there should be several extra tapes to
> > allow for schedule adjustments or disaster recov-
> > ery.
> >
> > So what is an "active tape cycle"? That is never defined anywhere.
>
> Bad wording. And it is seldom good practice to use a term (eg tapecycle)
> in the definition of the term.
> >
> > Although the last sentence is correct and it makes sense, it does not
> > explain how tapecycle should relate to the actual number of labeled
> > tapes.
> >
> > Here is my bad attempt at an improvement, please do not use it verbatim:
> >
> > You must have at least tapecycle tapes labeled, but you can have
> > more. By labeling extra tapes, you can allow for schedule
> > adjustments or disaster recovery. For example, lets say that your
> > tapecycle is set to 20 and you have 20 labeled tapes. If you
> > discover that tape #5 that you are about to put in the drive is bad,
> > your only alternative is to immediately label a new replacement
> > tape. If tapecycle was 20 and you had 25 labeled tapes, then you
> > could put tape #6 in the drive and deal with the problem later.
> >
> > On the other hand, if the number of labeled tapes greatly exceeds
> > tapecycle, then AMANDA (insert inefficiency issue here).
>
> Two things; I know of no inefficiency issues related to exceedingly
> large numbers of tapes in rotation. Or other problems, except cost,
> even in using fresh tapes every run. And as to your suggested
> revision, in writing man page documentation one must judge how much
> example, description, and definition should go into a document that
> is intended to be terse and quickly readable as reference, not how-to.
>
> Here is my attempt at a revision:
>
> tapecycle int
> Default: 15 tapes. Typically tapes are used by amanda in
> an ordered rotation. The tapecycle parameter defines the
> size of that rotation. The number of tapes in rotation must
> be larger than the number of tapes required for a complete
> dump cycle (see the dumpcycle parameter). This is calculated
> by multiplying the number of amdump runs per dump cycle
> (runspercycle parameter) times the number of tapes used per
> run (runtapes parameter). Typically two to four times this
> calculated number of tapes are in rotation.
>
> While amanda is always willing to use a new tape in its rotation,
> it refuses to reuse a tape until at least 'tapecycle' number of
> other tapes have been used. It is considered good administrative
> practice to set the tapecycle parameter slightly lower than the
> actual number of tapes in rotation. This allows the administrator
> to more easily cope with damaged or misplaced tapes or schedule
> adjustments that call for slight adjustments in the rotation order.
>
> --
> Jon H. LaBadie jon AT jgcomp DOT com
> JG Computing
> 4455 Province Line Road (609) 252-0159
> Princeton, NJ 08540-4322 (609) 683-7220 (fax)
---
Brian R Cuttler brian.cuttler AT wadsworth DOT org
Computer Systems Support (v) 518 486-1697
Wadsworth Center (f) 518 473-6384
NYS Department of Health Help Desk 518 473-0773
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