cideogniter部署到阿里云服务器出现session加载错误

A PHP Error was encounteredSeverity: Warning
Message: mkdir() [function.mkdir]: Invalid argument
Filename: drivers/Session_files_driver.php
Line Number: 117
Backtrace:

File: E:\amp\apache\htdocs\mvc\application\controllers\user.php
Line: 75
Function: library

File: E:\amp\apache\htdocs\mvc\index.php
Line: 292
Function: require_once

An uncaught Exception was encounteredType: Exception
Message: Session: Configured save path '' is not a directory, doesn't exist or cannot be created.
Filename: E:\amp\apache\htdocs\mvc\system\libraries\Session\drivers\Session_files_driver.php
Line Number: 119
Backtrace:

File: E:\amp\apache\htdocs\mvc\application\controllers\user.php
Line: 75
Function: library

File: E:\amp\apache\htdocs\mvc\index.php
Line: 292
Function: require_once

解决方法:

$config['sess_save_path'] =BASEPATH.'../'.'session_file';

session文件夹存在根目录下