Installation guide

42
Wi-Fi Location-Based Services—Design and Deployment Considerations
OL-11612-01
Installation and Configuration
History Archive Period
The history archive period (shown as “Archive For”) specifies the number of days that the location
appliance retains location history records for each enabled history collection category. The default
archive period is 30 days. Changes to the default history archive period should be done with careful
consideration after consultation with your Cisco field technical representative (or the Cisco Technical
Assistance Center), because longer history periods typically increase the amount of space consumed by
the location history database. Because newer history data within the archive period does not overwrite
older data, the combination of a large number of devices, an injudicious selection of history categories,
and an excessive history archive period can increase the risk of exhausting available free space.
To illustrate this point, you can approximately compare the amount of disk storage that is consumed
when selecting one combination of history category, archival period, and archival interval versus other
combinations. For example, take an environment consisting of 1100 WLAN clients, 300 asset tags, 20
rogue access points, and 30 rogue clients. Figure 26 indicates the effect of increasing the default archive
period to 365 days across the board and reducing the default history archive interval for clients (shown
in the table as “mobile devices”) and asset tags to 60 minutes (see Enable Asset Tag Polling on the
Location Appliance, page 96 and Figure 67) has on the amount of disk storage consumed.
Figure 26 Impact of History Interval and Archive Period on Database Size
Although the estimates shown in Figure 26 are only an approximation (they do not account for per record
display string sizes and database overhead, for example), you can see that database size increases from
about 30 MB to over 2.25 GB because of these changes in location history alone. The database backup
mechanism on the location appliance requires that there be this amount of free space available for
reliable extraction and compression of the database contents, thereby bringing the estimate to over 5 GB.
History Database Pruning
The data pruning parameters found under Location Server > Administration> History Parameters are
used to configure the location appliance to periodically prune duplicate data from its historical files to
free up disk space. The first data pruning event is configured to start at a preset number of hours and
minutes from when the system first starts collecting historical information. A repetition interval is also
configured on this screen and is specified in minutes. The default is for database pruning to occur once
a day.
Database pruning is especially important in situations where there is repeatedly high risk of running low
on available hard disk space (see Advanced Commands, page 43). When low available disk space
situations re-occur, more aggressive data pruning intervals may be warranted such that pruning occurs