TYPO3 Core

If you want to use t3lib_cache_backend_FileBackend for cache_pages or cache_pagesection you get the Exception 1231267498 (typo3/sysext/core/Classes/Cache/Backend/AbstractBackend.php Line 86). This happens because the LocalConfiguration-array ist overwritten with the DefaultConfiguration somewhere. And in DefaultConfiguration the option "compress" is set. And "compress" is no valid option for t3lib_cache_backend_FileBackend.
To work around this issue you have to set "$GLOBALS['TYPO3_CONF_VARS']['SYS']['caching']['cacheConfigurations']['cache_pages']['options'] = array();" in the AdditionalConfiguration.

Perhaps some other options for other cache backends produce this exception, too. I haven't testet that.

I don't know if this is really a bug, but at least it is very annoying and costed me some time to find out. :-)

LocalConfiguration:

...
    'SYS' => array(
        'caching' => array(
            'cacheConfigurations' => array(
                'cache_pages' => array(
                    'backend' => 't3lib_cache_backend_FileBackend',
                    'frontend' => 't3lib_cache_frontend_VariableFrontend',
                    'groups' => array('pages', 'all'),
                ),
                'cache_pagesection' => array(
                    'backend' => 't3lib_cache_backend_FileBackend',
                    'frontend' => 't3lib_cache_frontend_VariableFrontend',
                    'groups' => array('pages', 'all'),
                ),
...

P.S.: I know, the wiki says that the FileBackend should not be used for cache_pages (http://wiki.typo3.org/Caching_framework#Cache_configurations), but we have to. :-)