On Fri, 23 Mar 2007, Stephan Wiesand wrote:

> On Fri, 23 Mar 2007, Brett Viren wrote:
> 
> > Johan Mares <[log in to unmask]> writes:
> >
> >> If you have dual core 64 bits processors in your server. Is it
> >> recommended to install x86-64 version of a linux distro like SL ?
> >> What are the benefits ? Are there any disadvantages ? It would be for
> >> a LAMP, so would Apache or MySQL perform better or wouldn't they make
> >> no use of it ?
> >> Does anyone have any experience with this ?
> >
> > 32 bits: more software available, typically proprietary in nature.
> 
> Which often runs just as fine under the 64bit OS.
> 
> > Can access only <4GB RAM.
> 
> That's a common misconception. There's a per-process limit of 3 GB with 
> the standard kernel. But the system can have and use more memory. Even 
> 32-bit SL3 can handle at least 16GB with the ordinary -smp kernel.
> 
> > 64 bits: ~20% faster floating point (AMD only I believe), can access
> 
> Typically 20% faster for many scientific applications, with few 
> exceptions. A bit more than 20% with AMD CPUs. Not limited to floating 
> point processing.
> 
> IIRC, MySQL is one of those that do benefit but not that much. OpenSSL may 
> be anything from slightly slower to much much (several times!) faster, 
> depending on cipher and task. No clue how apache behaves.
> 
> 3GB per-process address space limit for 32-bit apps on SL3, 4GB on SL4.
> No (serious) such limit for 64-bit apps.
> 
> > more RAM than you can afford.  Potential compilation problems of
> > legacy code.
> 
> Usually, serious compilation and runtime problems of bad code, legacy or 
> not.
> 
> Larger memory footprint, depending on application and payload.

It is common for large databases that use lots of memory to use 64 bit .  
It make the memory usage of the program faster and easier.

-Connie Sieh

> 
> 
> The last two probably don't apply to a LAMP. I'd personally go for x86-64.
> 
> 
> Regards,
>  	Stephan
> 
>