Using a clone to upgrade a Virtual Machine

Question

If I'm planning on upgrading a server application, what is a good way of getting network access, while preventing duplicate network names or other side effects?

The current process I was going to try consists of the following:

1. Shut down the original VM (call it SRV)
2. Clone the VM (call it TMP)
3. Restart SRV (so service is resumed)
4. Reconfigure TMP so the network adapter is isolated (disconnected, or on a test network)
5. Power on TMP
6. Connect to TMP (from the vSphere console for example, if it has no network)
7. Upgrade the software on TMP
8. Shut down TMP
9. Reconfigure TMP so the network adapter is live again
10. Shut down SRV
11. Power up TMP
12. Rename VM SRV to OLD
13. Rename VM TMP to SRV

This assumes that there is no data being gathered by SRV that is needed during the switch-over period. If there is (log data for example, then this is probably not the right way to do things

If I want the server to be on the network after step 5, is my only option

• run sysprep on it and give it a new SID
• rename it SERVER-TMP
• change the IP to an unused address

Then when ready to go live:

• remove old server from domain
• rename SERVER-TMP to SERVER
• change the IP to the production IP

Answer 1

That would provide for a very smaller outage but seems like a lot of work and you would risk the possibility of lost data. Also some applications tie their licensing to the servers name, IP, or MAC address which could be affected by this (cloning a VM gives it a new MAC address). Having the wrong host name could also mess up the application (web services with virtual hosts).

Your best bet to try something like this would be to have a VLAN that you could run the TMP VM on while you performed the update. Then when you're all done you would shut down the live VM and switch the network on the TMP server. A downside to this is that you might need to have additional duplicate servers in this VLAN (domain controller, DNS, etc.).

The process we usually follow to perform an update is the following:

1. Schedule an outage of the service
2. Take a snapshot of the VM
3. Install the update(s)
4. Verify that everything is working correctly (I usually wait two business days).
5. Delete the snapshot (there are performance issues with snapshots so you want to get rid of them)