Hi Rob,
I have just gone through this exact exercise at home. I am running 
Ubuntu Hardy 8.04.1 64-bit workstation as a host operation system and 
Vmware server with 6 virtual machines as guests.
  - 5x Ubuntu Hardy 8.04.1 servers for development, testing, media 
serving, hosting, etc.
  - 1x  Windows XP Professional for managing hardware devices that Linux 
does not support.
I bought refurbished Dell T7400 which has 2x 2.66Ghz Intel Xeon E5430 (8 
cores), 32 GB DDR2 ECC Fully Buffered FLS RAM and a clutch of SATA 
disks. Do checkout the refurbished kit suppliers you can get significant 
savings!
A1 - What Hugo said is dead right.
Just make sure that you get the right hardware -- check the
"AMD-V" or "Intel-VT" capabilities on the relevant processor lists on
Wikipedia.
I decided to go with Vmware since we use Vmware at work and it is what I 
am most familiar with, plus it can exploit the Intel-VT capabilities in 
my box. In addition to getting kit with either Intel-VT or AMD-V, your 
strategy is basically sound, except I decided fastest CPUs were not as 
valuable as the number of cores. So I went for lower CPU and bus speeds 
in preference for more cores and more RAM. From my monitoring of servers 
at work RAM is the more useful commodity in a server and I have little 
need for prolonged periods of CPU intensive activities.
A2 - What Vic said is dead right.
The 32-bit hugemem kernels from RHEL will address 64GB. For RHEL3, you got
a 4GB limit per process - I doubt that's changed, but I don't actually
know for sure.
So you can use a 32-bit kernel and I did test this and it does work, 
plus you can even avoid some minor incompatibilities with some (desktop) 
applications that are still flaky in their 64-bit flavours. In the end I 
decided to go with a 64-bit host OS and deal with the minor niggles of 
64-bit Java plugins, Real Player 11, etc.
Most of the current crop of virtualisation technologies can exploit 
AMD-V or Intel-VT. See the link below for details and choose the one 
suits you need best.
 * 
http://en.wikipedia.org/wiki/X86_virtualization
Good luck with your project. I hope you have as much fun as I did :-)
Regards, Martin.
Rob Malpass wrote:
> Hi all
>  
> I need some pretty basic advice on building a new box specifically for 
> the purposes of virtualisation (running about 3 servers).   My current 
> Sempron 3200+ with 2Gb of RAM isn't cutting it.   So, without the 
> funds to go really top end, I'm going for the fastest CPU I can afford 
> and give it plenty of RAM.   Q1 - is this a good strategy for 
> virtualisation?
>  
> Q2 Do I have to run a 64-bit kernel to address all 6Gb (if I go for 
> that much) RAM?   I heard a while back that XP can't handle anything 
> over 2Gb without patching - not sure about Vista.   Probably an 
> academic debate because I intend to run Ubuntu - but I wanted to check 
> whether it had the same restriction.   The problem is that the 
> graphics card I have in mind (bought for 80UKP last year) didn't work 
> well with 64-bit Ubuntu or Fedora - though that's probably fixed by 
> now.   Running in 32-bit mode (both distros) was fine - but would 
> obviously be self defeating if I can only address 1/3 of my RAM as a 
> result of running in 32-bit mode.
>  
> Basic questions for a Monday morning I know but a bit of sage advice 
> here could save me a lot of time and money.
>  
> Thanks in advance (as always).
>  
> Cheers
> Rob
> ------------------------------------------------------------------------
>
> This body part will be downloaded on demand.