I would like to know if I can have a OneClick instance running on Centos 7 while all my Spectrum servers are on RH6.
If yes, I would also like to know if there is any restriction regarding running OneClick on a VM (all our servers are currently running only on bare metal).
Currently we only support Redhat Enterprise Linux 6.x and 7.x. (Note 5.x supports up to 10.2.1).
There are no restrictions on running any Spectrum installation in a virtualized environment.
Hope this helps!
From a technical PoV, you can run CA Spectrum under CentOS - in the same way that RHEL runs. This includes having OneClick/MLS/LS on any combination of OSs and versions. However, I would highly recommend that for management purposes that you stick with one OS (better yet, under a supported OS). That way this eliminates the chance that issues that you may see are not OS related. Also, having the same OS makes patching a lot easier!