[CentOS] cobbler installation of CentOS-5.5

[David Sommerseth]

On 28/03/11 16:49, Timothy Murphy wrote:
> I'm trying to install CentOS-5.5 on my new HP micro-server,
> which has no CD drive.
> 
> I've set up cobbler and cobbler-web on my old server,
> and can access cobbler-web from my laptop.
> 
> I have 3 queries about the installation.
> 
> 1. Is there any advantage is using the 64-bit CentOS
> rather than 32-bit?

Yes, there are advantages to use 64-bit instead of 32-bit.  But it also
depends on how much memory you have.  If you have more that 4GB RAM, you
should really not depend on 32-bit at all.  This is a hardware limit on the
CPU level.  However, Intel did enable some hacks to make it possible to use
more than 4GB RAM on the IA32 based CPUs.  Those are mostly known as PAE
enabled kernels.  But few kernel developer really likes PAE.

Another limitation is that 32-bit applications have limited memory
available compared to a 64-bit application.  PAE might even slow down the
kernel.

Don't go PAE if you can go 64-bit.  There are really no good reasons why
not to use 64-bit today.  There are quite few software packages which is
not ready for 64 bit nowadays, and those should rather be fixed than to
keep users back on 32 bit.

If you for some reason need to run 32-bit user stack, it is even possible
to install and a 64 bit kernel on a 100% 32-bit user space.  And a running
32-bit applications in a 64-bit setup is possible, as long as you have the
32-bit glibc and other needed support libraries installed.  However, 32-bit
applications have the same memory limitation when running.

For some brief PAE discussion, see here:
<http://www.held.org.il/blog/2008/07/pae-whats-that-and-how-bad-for-performance/>
<http://kerneltrap.org/node/3816>
<http://www.linuxquestions.org/questions/linux-general-1/32-bit-os-and-4gb-memory-limit-707762/>

Having all this said, RHEL supports up to 16GB with PAE on 32bit, thus
CentOS will do the same.  However, if can avoid it and install 64-bit, I
recommend you to do that instead.  PAE is really dying, and you'll likely
have more issues with PAE than 64-bit in the long run.


kind regards,

David Sommerseth