The ProxySG appliance can establish a successful connection with the FTP server and a test test upload works but main upload fails.
The appliance generates event log alerts for failed FTP uploads. Event log details might show events such as the following (this in an example of FTP upload used in streaming access log):
220 Microsoft FTP Service"
331 Password required for bcftpupload."
230 User bcftpupload logged in."
250 CWD command successful."
200 Type set to I."
227 Entering Passive Mode (172,23,45,101,173,239)
Creating data socket to 172.23.45.101:44527"
125 Data connection already open; Transfer starting."
426 Connection closed; transfer aborted."
Client received bad transfer response - 426."
Log uploading failed.
In this example, FTP response code 426 means “Transient Negative Completion reply” from FTP server. A successful upload should display 226, meaning “Transfer complete”. If the status code is in 4XX format, most likely the FTP server does not have sufficient disk space to write the log file. In case of test upload, the appliance uploads a dummy file 1KB in size and shows response code 220. The original log file is larger than that.
For information on FTP response codes, refer to http://en.wikipedia.org/wiki/List_of_FTP_server_return_codes.