The primary goal of Virtualization is to enable you to bring up the overall utilization of hardware by combining a bunch of low utilizated systems onto a single piece of hardware.
The secondary goal is typically to gain hardware independance for applications.
The third goal is typically High Availability
With oracle databases this big combined with the performance requirements you need to be able to get out of the disk for regular activity as well as backups, as well as the processor and RAM requirements that you'd also be running alot of other VM's on the same hardware unless your current ESX farm is pretty massive.
In my environment I could probably virtualize something like that but I'd probably then have to pay about 70k to put in another esx server to regain the virtualization space used up by a the 3 oracle instances as well as the
On the other hand a 20k server including O/S with a couple quad core intel processors and 32GB of RAM would more then suffice for the Oracle environment and leave me room to virtualize another 10 VM's or more in my current environment.
Not saying you shouldn't do it, but you have to really consider what you are trying to gain with the virtualization and if the added cost both from a monetary (ESX isn't cheap) and virtualization performance loss provides a big enough Return on investment to virtualize.
In my environment I have 3 solaris servers running oracle. I would have an outage if I lost any one of the servers, but within 4 hours I could rezone/remount the oracle luns on any of the other servers and recover the databases and suffer no performance loss (although we have 2 hour response on the physical hardware anyhow).
Not as fast as using ESX HA, but in our environment, the virtualization capacity we'd lose by virtualizing the oracle was of more importance then the cost of the oracle servers.
