FlexiCache is a fast, full-featured and flexible caching system which will improve the performance and availability of any WordPress site
FlexiCache stores config and cache data within the plugin directory (see plugin documentation in versions 220.127.116.11 onwards for the reason why).
If you upgrade the plugin using WordPress's built-in upgrade process, the entire plugin directory will be replaced, including your config and cache data.
To preserve these, take a copy of the "plugins/FlexiCache/_data" directory before upgrading, and then copy it back after the upgrade is complete.
If you upgrade directly via SVN, this should not be required, since only the files under version control will be updated.
FlexiCache can be disabled via the admin interface as with any plugin, however if you are running in Standalone mode, you should remove the .htaccess modifications before deactivating the plugin.
For a standard WordPress install, this modification can be done via the admin interface, however it is recommended that you make this change manually, especially if using WordPress MU, where multiple sites may share the same .htaccess file.
Please see the documentation supplied with the plugin (accessible via WordPress's admin interface) for more information.