To read a file from the MSS, issue your FTP Client's normal command to retrieve a file from an FTP server. If the file is not in the cache, it will notify you that it is being fetched from the MSS. You can expect a delay while this happens, and the data transfer to your FTP Client will not start until the entire file is in the cache. For example:

ftp> get ftptest2
local: ftptest2 remote: ftptest2
200 PORT command ok.
125-Fetching file from MSS.
125 Data connection open; transfer starting.
226 Binary Transfer complete.
359984 bytes received in 0.00293 secs (1.2e+05 Kbytes/sec)