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Migration from ESX 3.5 (w/o downtime?)


I have a VC 3.5 server, few ESX hosts(Clustered)

I am migrating to Vsphere 4. I am setting up VCenter on new server, is it possible to unregister the ESX 3.5 host(with VM running) from VC 2.5, and register the ESX 3.5 host in VCenter 4.0 without restart?

After that, I will need to VMotion between 3.5 host to 4.0 host for those VM that I want to migrate, and subsequently decomission the ESX 3.5 server.

Do you guys foresee any problem in doing so? Thanks!

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We did exactly that on my office.

Migration was from a 4node ESX3.5 setup with VC2.5 (on Win2K3 32bit) with local SQL, to ESX4i a new VC4 (Win2K8, 64bit) connected to our Oracle.

Did following steps.

0) Get you VC4 licenses in order first. Pitfall: you "only" have 60 days to do if afterwards

1) Installed a fresh VC4, this time connected to our Oracle. Pitfall to know about: Win2K8 R2 DOESN'T work (ADAM failing), you need ie Win2K8 SP2.

2) "Remove" our test-ESX from VC2.5 and "connect to" our VC4 server. Pitfall : You still need the VC2.5 licenseing server and configure VC4 to use it.

3) "Remove" our ESX-server running "preproduction" virtual machines first. "Connect to" our VC4. Pitfal: Do keep the folder/resorce pool structure

4) "Remove" our ESX-server running "production" virtual machines last. "Connect to" our VC4.

5) VERY IMPORTANT: Remember to tell your sysadmins not to "upgrade virtual hardware" without first installing new Vmware tools.

5) Enable "Maintenance" on one ESX-server at the time. Did a fresh install with ESX4i. Pitfall: Remember to enable SSH if you use it.

6) You are done! Now you can start using the new features (distributed switch etc...) Also, you can clean up/stop the VC2,5 server.

We did this over a longer period (about a month) just to check how virtual machines would behave when we upgraded from ESX3.5 to ESXi4.

Installing ESXi on a USB-stick gave us the possibility to quickly reverse to ESX3.5 if we needed, just by changing boot device and pointing to the old VC2.5.

Sure, we lost all our preformance statistics but we don't use any longer history if not troubleshooting something.

Another thing we did was to connect the VCenter to our Windows AD, something we didn't have last time around.

One anoying thing was that you actualy have to "remove" the ESX3.5 server from VC2.5 before connecting to VC4, even thou you use the same license server.

I would like to have seen that you are able to do directly or the server becoming "evaluation" license first.

Also, check you resource pools after connecting to VC4.

I noticed that some pools have totaly incorrect resource limitations and some have a resource reservation that didn't exist before.

It is easily fixed by changing the limitation but to get rid of the reservation you have to create new reservation pools (for some reason).

And no, we didn't have any serious problems beside the smaller problems and pitfall mentioned above.

Especialy having to reinstall Win2K8 after trying VC4 to install on Win2K8 R2 was realy annoying.

But Vmware compatibility clearly states that R2 isn't supported so it was my own fault.

Hope this helpes you. on the way

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