We have an FTP Server (via IIS) running Server 2003 and I need to migrate to Server 2008. DNS TTL is set to 1 hour. It's an FTP server so I'd like to have as little down time as possible. The business use AS400 systems and various systems (not just Windows) to transfer files via FTP so I need to take into account a lot of people will not reboot or flush DNS.
I have already checked with the business and the good news is no one appears to be using the IP Address for the physical FTP Server running Server 2003. All FTP jobs are using the host name only. Management wish me to use a cname (Alias) so remaming the server to match to old host name is not an option so I intend to create a CNAME to match the old server (after it is renamed) andhave the cname point to the new FTP Server IP Address. My implementation steps are below:
Old server Name: FTPSrv1 (running server 2003)
New Server Name: FTPSrv2 (running server 2008 R2) - different IP address
1. Rename old sever, FTPSrv1, to FTPSrv1_old first*
2. Delete the A record for old FTP Server (FTPSrv1) in DNS
3. Create a new DNS CNAME in DNS. Cname will point to new FTP Server running Serve 2008, FTPSrv2
As business make reference to host name only they will use cached information to connect to old and when DNS kicks in, use the alias. I guess the only down time is the time I bring down the old server, FTPSrv1, to rename it as I do not believe I can create a Cname/ alias with the same name as the physical server with out renaming it first but please confirm.
Any flaws in this plan? Again, I can not guarantee reboot or people flushing DNS and would like to have as little down time as possible to avoid FTP transfers failing so an advice appreciated.
Thanks in advance.