SSO wont load the vCenter Server much until unless there are too many users administrate vCenter or connect to vCenter for managing. SSO performance is a
We are running SSO and vCenter on same VM and its running absolutely fine so far.
Also consider these answers in FAQ. http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=2034918
Why would I install SSO on a separate machine from vCenter Server?
If SSO is on the same machine as one of your vCenter Servers, and the machine goes down, you will lose not only that vCenter Server, but also the ability to log into all your other vCenter Servers.
Why would I install SSO on the same machine as vCenter Server?
vCenter and SSO on the same machine is the default configuration, if you have only one vCenter Server instance.
How many vCenter Servers can an SSO instance serve?
SSO poses no restriction on the number of vCenter Servers registered to it.