x86 vs. x86_64

[Eric Shubert]

First off, I believe that the limit w/out PAE is 3G. I'm running ubuntu 
LTS (8.04) 32-bit with 2.6.24-27-generic, Intel T7700 processor 
(64-bit), with 4G of ram. "free" shows 3106560 total mem. Rather than 
bother with the PAE kernel, I'm simply going to load the 64-bit version 
of LTS 10.04 when it comes out, since I'll be wanting to test 64-bit 
guest servers (need 64-bit host to run 64-bit guests with VMware).

Alex Dean wrote:
> This has always confused me a bit, so it seems like a good time to ask.

You're not alone there. ;)

> I have a machine running 32-bit Ubuntu.  It has 4GB of RAM.  I'd like to 
> use it as a host OS for several (maybe 6?) VM guests.  I thought it 
> would make sense to add more RAM before doing this, but I wasn't sure if 
> I'd be able to utilize the extra memory w/o changing to a 64-bit host 
> OS.  From reading this thread, it sound like I wouldn't need to change 
> over to a 64-bit host, since none of my guests would have processes 
> accessing more than 4GB of RAM.  Is that correct?

Yes.

> The guests will be server OSs, not running any GUI applications, so I 
> expect their resource utilization to be pretty slim.  I just need 
> somewhere to test multiple-box HA cluster configurations, and I don't 
> have the extra hardware lying around to do it with.

Sounds like a viable plan. (Then again, Custer had a plan.) ;)

> I'll probably use VMWare, but that's not settled.  If OpenVZ or 
> VirtualBox might have advantages for this kind of thing, I'm interested 
> in hearing about them. The host is Ubuntu, but the guests will be RHEL5, 
> so I think that means I can't use OpenVZ since they'll have different 
> kernel versions.  Someone correct me if I've got that wrong.

I don't know about OpenVZ.

I haven't used VirtualBox, but my understanding is that it's geared more 
toward workstation guests. Also its development is slightly behind 
VMware in some areas (eg USB).

I do use VMware Server(2) and VMware Player, and am quite happy with 
them. You should be aware though, that you'll need to do some 
configuration tuning in order to get VMware running optimally, 
performance wise. There is a bit of a learning curve there.

-- 
-Eric 'shubes'