10g RAC design options

Currently we are using 2 x Sun Fire 15K 8 CPU_at_1.2GHz 16GB of Memory under VCS 3.5 with Solaris 8, we run both nodes active-active and failover between both, each node has 4 Oracle instances, if all instances try to run on one node the performance is impacted severely, and this will probably always be the case so scaling up is no longer an option.

In another 4-6 months this environment wont be able to support the future application requirements so RAC is starting to look very good at this point, I'm strongly looking to go with a 4 Node 4-way x86 server w/8GB of memory from either Sun or IBM, Sun is currently shipping Opterons which are 64bit but I'm not sure if Linux would be a better option is 64bit Linux ready for primetime? What is the status of Oracle 10g RAC on 64bit x86 Solaris?

Most of the staff is very Solaris savvy which is why Solaris looks like a much better fit, I do not want to go with a sparc based solution because of the high cost of Oracle licenses and slow CPU performance compared to x86.

Another concern; uptime have been almost 99.999% over the past 3+ years my current solution has been deployed, how are most people deploying RAC? Do you cluster between RAC using VCS? I've read that their can be certain situations where patching RAC would require every node being offline, in this environment this is not a suitable option.

I have been consulting with Oracle but I would just like to hear from real world situations.

Thanks

-- 
Rodrick R. Brown
Systems Architect
http://www.rodrickbrown.com
rodrick.brown[@]gmail.com