Provided by: amanda-common_3.3.0-1ubuntu1_i386 bug

NAME

       amanda-taperscan - Amanda Taperscan Algorithms

DESCRIPTION

       Amanda uses a taperscan algorithm to select volumes on which to store
       dumps. Historically Amanda has provided only one, fairly complex
       taperscan algorithm, but this algorithm did not suit the needs of all
       users. Now Amanda offers a wide array of algorithms to suit varied
       needs. Adding new algorithms is not difficult.

       The taperscan algorithm is specified with the taperscan parameter,
       which has a default value of traditional.

       Taperscan algorithms are implemented as perl packages with the prefix
       Amanda::Taper::Scan::. See the perl documentation for
       Amanda::Taper::Scan for more information.

DEFINING A TAPERSCAN

       An taperscan is defined in amanda.conf(5) as follows:

       define taperscan $taperscan_name {
          comment "$comment"
          plugin "$pluginname"
          property "$PROPERTY_NAME" "$PROPERTY_VALUE"
          ...
       }
       and then referenced in the global section as

         taperscan "$taperscan_name"

       Taperscan properties, like Amanda configuration parameters, are
       insensitive to case, and - (dash) and _ (underscore) may be used
       interchangeably.

       See the individual plugin documentation below for properties applicable
       to each plugin.

TAPERSCAN ALGORITHMS

       In general, these algorithms will only select reusable volumes. These
       are volumes which are listed in the tapelist(5) with the reuse flag,
       and which are not among the tapecycle-1 most recent volumes in the
       list. Put another way, reusable volumes do not contain data that must
       be retained. Note that if fewer than tapecycle-1 volumes have been
       written then there are no reusable volumes. Newly labeled volumes
       (volumes that have been labeled with amlabel but never used) are
       considered reusable.

       Many of these algorithms look for the oldest reusable volume. In most
       cases, this is the best volume to overwrite, as the data it contains is
       older than that on any other volume. If there are no reusable volumes,
       then there is no oldest reusable volume.

   traditional
       This algorithm duplicates Amanda's historical behavior, and it operates
       in two stages.

       First, if there is an oldest reusable volume and if the changer
       supports "fast" searches, then the algorithm uses the changer to search
       for that volume. Newly labeled volumes are not considered when
       calculating the oldest reusable volume. Consequently, this taperscan
       algorithm prefers volumes which have been used before to newly-labeled
       volumes when a fast-searchable changer is in use.

       Second, if there is no oldest reusable volume, or if that volume is not
       available in the changer, then the algorithm begins a sequential scan
       of the changer, starting at the current slot. It selects the first
       suitable volume it finds: a reusable volume (perhaps newly-labeled) or,
       if autolabel includes empty, a blank volume. Even across multiple
       invocations (when runtapes > 1), it will not return the same slot
       twice.

           Note
           This algorithm shows an undue preference for volumes already
           containing data, by omitting newly-labeled volumes from its first
           stage.  Historically, many Amanda changer scripts were not
           fast-searchable (including chg-multi, chg-disk and, if
           havereader=0, chg-zd-mtx), and thus skipped the first stage,
           allowing new volumes to find their way into the tape cycle.  New
           changers are almost all fast-searchable, so both stages of the
           algorithm are used and new tapes may be unexpectedly excluded.  If
           this causes an undesirable change in behavior, consider one of the
           other taperscan algorithms..sp .5v

   oldest
       This algorithm works with the Changer API (see amanda-changers(7)),
       using the inventory returned by the changer to locate the oldest
       acceptable volume available. Note that this will not work with changers
       that do not support inventory (old changers). The algorithms scans
       unknown slots only if no known usable volume is found in the inventory.

       An acceptable volume is a reusable volume, a new labeled volume or an
       unlabeled volume that can be labeled according to autolabel. Note that
       changers do not always know the contents of every slot - for example, a
       tape with an unknown barcode will not be considered usable.

       Use amtape CONF inventory to see the changer's inventory, and use
       amtape CONF update to update it.

   lexical
       This algorithm also works with the Changer API, using the inventory to
       determine the acceptable volumes; it then uses the volume which follows
       the last-used volume in lexical order. For volume labels containing
       leading zeros, e.g., CORP-010, this algorithm will run through the
       volumes in the natural order.

       It scans unknown slots only if no usable volume is found in the
       inventory.

       See oldest, above, for a definition of acceptable volumes.

       >>>>>>> 6a40a39... manpage edits

SEE ALSO

       amanda(8), amanda.conf(5), tapelist(5), amanda-changers(7), amanda-
       interactivity(7)

       The Amanda Wiki: : http://wiki.zmanda.com/

AUTHOR

       Dustin J. Mitchell <dustin@zmanda.com>
           Zmanda, Inc. (http://www.zmanda.com)