Cache Log Error Levels
The log messages in the cache drvier's is_supported calls are more suited for the debug level.
diff --git a/system/libraries/Cache/drivers/Cache_redis.php b/system/libraries/Cache/drivers/Cache_redis.php
index 484f284..40823fc 100644
--- a/system/libraries/Cache/drivers/Cache_redis.php
+++ b/system/libraries/Cache/drivers/Cache_redis.php
@@ -168,7 +168,7 @@
 		}
 		else
 		{
-			log_message('error', 'The Redis extension must be loaded to use Redis cache.');
+			log_message('debug', 'The Redis extension must be loaded to use Redis cache.');
 			return FALSE;
 		}
 	}