1AMANDA-TAPERSCAN(7)               Miscellanea              AMANDA-TAPERSCAN(7)


6       amanda-taperscan - Amanda Taperscan Algorithms


9       Amanda uses a taperscan algorithm to select volumes on which to store
10       dumps. Historically Amanda has provided only one, fairly complex
11       taperscan algorithm, but this algorithm did not suit the needs of all
12       users. Now Amanda offers a wide array of algorithms to suit varied
13       needs. Adding new algorithms is not difficult.
15       The taperscan algorithm is specified with the taperscan parameter,
16       which has a default value of traditional.
18       Taperscan algorithms are implemented as perl packages with the prefix
19       Amanda::Taper::Scan::. See the perl documentation for
20       Amanda::Taper::Scan for more information.


23       An taperscan is defined in amanda.conf(5) as follows:
25       define taperscan $taperscan_name {
26          comment "$comment"
27          plugin "$pluginname"
28          property "$PROPERTY_NAME" "$PROPERTY_VALUE"
29          ...
30       }
31       and then referenced in the global section as
33         taperscan "$taperscan_name"
35       Taperscan properties, like Amanda configuration parameters, are
36       insensitive to case, and - (dash) and _ (underscore) may be used
37       interchangeably.
39       See the individual plugin documentation below for properties applicable
40       to each plugin.


43       In general, these algorithms will only select reusable volumes. These
44       are volumes which are listed in the tapelist(5) with the reuse flag,
45       and which are not among the tapecycle-1 most recent volumes in the
46       list. Put another way, reusable volumes do not contain data that must
47       be retained. Note that if fewer than tapecycle-1 volumes have been
48       written then there are no reusable volumes. Newly labeled volumes
49       (volumes that have been labeled with amlabel but never used) are
50       considered reusable.
52       Many of these algorithms look for the oldest reusable volume. In most
53       cases, this is the best volume to overwrite, as the data it contains is
54       older than that on any other volume. If there are no reusable volumes,
55       then there is no oldest reusable volume.
57   traditional
58       This algorithm duplicates Amanda's historical behavior, and it operates
59       in two stages.
61       First, if there is an oldest reusable volume and if the changer
62       supports "fast" searches, then the algorithm uses the changer to search
63       for that volume. Newly labeled volumes are not considered when
64       calculating the oldest reusable volume. Consequently, this taperscan
65       algorithm prefers volumes which have been used before to newly-labeled
66       volumes when a fast-searchable changer is in use.
68       Second, if there is no oldest reusable volume, or if that volume is not
69       available in the changer, then the algorithm begins a sequential scan
70       of the changer, starting at the current slot. It selects the first
71       suitable volume it finds: a reusable volume (perhaps newly-labeled) or,
72       if autolabel includes empty, a blank volume. Even across multiple
73       invocations (when runtapes > 1), it will not return the same slot
74       twice.
76           Note
77           This algorithm shows an undue preference for volumes already
78           containing data, by omitting newly-labeled volumes from its first
79           stage.  Historically, many Amanda changer scripts were not
80           fast-searchable (including chg-multi, chg-disk and, if
81           havereader=0, chg-zd-mtx), and thus skipped the first stage,
82           allowing new volumes to find their way into the tape cycle.  New
83           changers are almost all fast-searchable, so both stages of the
84           algorithm are used and new tapes may be unexpectedly excluded.  If
85           this causes an undesirable change in behavior, consider one of the
86           other taperscan algorithms..sp .5v
88   oldest
89       This algorithm works with the Changer API (see amanda-changers(7)),
90       using the inventory returned by the changer to locate the oldest
91       acceptable volume available. Note that this will not work with changers
92       that do not support inventory (old changers). The algorithms scans
93       unknown slots only if no known usable volume is found in the inventory.
95       An acceptable volume is a reusable volume, a new labeled volume or an
96       unlabeled volume that can be labeled according to autolabel. Note that
97       changers do not always know the contents of every slot - for example, a
98       tape with an unknown barcode will not be considered usable.
100       Use amtape CONF inventory to see the changer's inventory, and use
101       amtape CONF update to update it.
103   lexical
104       This algorithm also works with the Changer API, using the inventory to
105       determine the acceptable volumes; it then uses the volume which follows
106       the last-used volume in lexical order. For volume labels containing
107       leading zeros, e.g., CORP-010, this algorithm will run through the
108       volumes in the natural order.
110       It scans unknown slots only if no usable volume is found in the
111       inventory.
113       See oldest, above, for a definition of acceptable volumes.


116       amanda(8), amanda.conf(5), tapelist(5), amanda-changers(7), amanda-
117       interactivity(7)
119       The Amanda Wiki: : http://wiki.zmanda.com/


122       Dustin J. Mitchell <dustin@zmanda.com>
123           Zmanda, Inc. (http://www.zmanda.com)
127Amanda 3.5.1                      12/01/2017               AMANDA-TAPERSCAN(7)