Omeka Has Encountered an Error

Zend_Session::start() - /websites/southafricaarchive.org/application/libraries/Zend/Session.php(Line:479): Error #2 session_start(): open(/websites/southafricaarchive.org/var/phpsessions/sess_8vnh1limfn92rf9vr345r3ri22, O_RDWR) failed: No space left on device (28) Array /websites/southafricaarchive.org/application/libraries/Zend/Session.php(Line:489): Error #2 session_write_close(): open(/websites/southafricaarchive.org/var/phpsessions/sess_8vnh1limfn92rf9vr345r3ri22, O_RDWR) failed: No space left on device (28) Array /websites/southafricaarchive.org/application/libraries/Zend/Session.php(Line:489): Error #2 session_write_close(): Failed to write session data (files). Please verify that the current setting of session.save_path is correct (/websites/southafricaarchive.org/var/phpsessions) Array