Re: vcenter configured as VM

Benefits of having a separate management cluster resources (for vCenter Server, vCenter Database, etc) are enhanced security and capacity & resource management isolation.

The primary disadvantage of creating a management cluster is cost. You must have a large enough environment to warrant a dedicated management cluster.

e.g. 3 hosts for management cluster would add significant cost to an infrastructure of only 10 hosts but it would proportionally add little cost to an infrastructure of 50 hosts.

There are some good blog post regarding separate management cluster, see below

http://longwhiteclouds.com/2013/04/09/best-practice-architecture-for-your-vsphere-environment-build-a-management-cluster/

http://www.vifx.co.nz/best-practise-for-your-management-cluster

http://download3.vmware.com/vcat/documentation-center/index.html#page/Architecting%20a%20vCloud/3a%20Architecting%20a%20VMware%20vCloud.2.010.html

You can also create a separate resource pool for the management VMs if you do not have separate hosts for management cluster.

Properly design and monitor closely when using resource pools.

Avoid making resource pools and virtual machines siblings in a hierarchy to avoid unexpected performance.