Restore of a 1.0 backup to Cisco Unity Express (CUE) version 1.1.1 results in this error message:
Connection to backup server failed: ftp://<ip address and path for ftp server>:
Transfer failed: Error in reading/writing to backup server.
The history log file on the FTP server (history.log) is also successfully updated with this failure information.
The FTP server's own log can show that CUE gave up downloading further Data and Configuration backup files after attempting to download the VoiceMail_pre_op.backup file and finished by modifying history.log.
In contrast, a backup and restore of the existing 1.1.1 CUE is successful. This fact is important since the VoiceMail_pre_op.backup file is present in version 1.1.1 but not present in version 1.0 of CUE. The restore program checks for its availability to determine the version.
CUE is designed to handle the return code of 550; "Requested action not taken. File unavailable" (file not found, no access) if the VoiceMail_pre_op.backup file does not exist on the server. If it receives a return code 550, it assumes a restore of a version 1.0.2 backup is required and takes appropriate action.
Unfortunately, some FTP servers return something other than error code 550 when a file is missing. Some have been known to return 501, indicating a syntax error in parameters or arguments.
When CUE receives error 501, it assumes that the file exists and the file transfer has failed, resulting in the restore failing.
A workaround to this problem is to use an FTP server which does return error code 550. One example is the GuildFTP server available at GuildFTPd.