Re: 32-bit vs AMD64 on Opteron for LAMP server
On July 6, 2007 07:29 am michael@estone.ca wrote:
> Quoting Neil Gunton <neil@nilspace.com>:
> > michael@estone.ca wrote:
> >> I don't have any facts or numbers to bring forward, but you probably
> >> won't notice that much of a difference.
> >
> > What do you base this opinion on?
>
> Nothing really,
> I've setup a handful of amd64 servers and a whack of i386 ones.
> Alot of them web servers running basic php and mysql stuff.
> Speeds "felt" the same.
>
> >> Having said that, I would say go for the AMD64 port.
> >> I don't think the install is anywhere near less
> >> straightforward than the 32bit port.
> >
> > The AMD64 port is less straightforward because they do not include
> > the dpt_i2o driver, which is necessary for my RAID card. Instead, I
> > have to either use the i2o_block driver, which I gather has had some
> > reliability issues under load, or else build a patched kernel with
> > dpt_i2o, which isn't ideal since it always complicates and lengthens
> > the install. Also, for some reason, my own kernels always seem to end
> > up being slower than the stock kernels, even though I am careful to
> > go through and build in/enable everything very specific to the
> > hardware.
>
> Ah, yes. If your missing some hardware drivers, it can be a pain.
>
> >> But since you are running 4 Gig of RAM, take full advantage of it by
> >> running amd64.
> >
> > My understanding is that 32-bit can utilize up to 4 GB as well, it's
> > when you have more than 4GB that it starts to matter.
>
> I always thought that 32 bit sarge with 4G ram, would only show about
> 3.3G of available RAM. I could be wrong, and perhaps this doesn't
> happen in etch.
Depends on the motherboard. The top 256-768 MB of RAM is reserved for PCI
mapped memory space and other devices. Some motherboards and CPUs let
you re-map this memory above the 4 GB boundary (making it appear that you
have up to 5 GB of RAM) while others don't. AMD systems tend to be
better in allowing the remapping.
32-bit systems can use 3 GB without problems. It's when you have more
than 3 GB that things start to get weird.
64-bit systems don't have these issues.
--
Freddie Cash, LPIC-2 CCNT CCLP Network Support Technician
School District 73 (250) 377-HELP [377-4357]
fcash-ml@sd73.bc.ca
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