32-bit vs AMD64 on Opteron for LAMP server
Hi all,
I am going to be rebuilding a server in August which has been running
Sarge AMD64 for the last couple of years in a colo environment. I am
going to do a total rebuild (need to repartition the disks). Since I am
using the dpt_i2o drivers for Adaptec RAID, which I had a hell of a
problem getting to work under Sarge AMD64 (and still aren't in the
default modules for Etch), I am considering all options, including
simply using 32-bit Etch on the new install. This is a LAMP server,
running apache 1.3, mysql 5.
I am aware of some of the benefits of running 64-bit vs 32-bit on an
Opteron system, including larger memory addressing, more registers and
possibly better performance with larger numbers of connections.
However, I am wondering if anyone has actual experience of running a
real-world LAMP server, on the same hardware, using the same system,
using both 32-bit and 64-bit (not at the same time obviously!). In other
words, does anyone have real-world experience of whether AMD64 benefits
are really apparent to this kind of application. I currently have 4GB
RAM on the server, and no intention to upgrade it soon. I think the disk
I/O will become an issue way before memory does (even with kernel disk
caching, it's just the impression I get from current experience on my
site with upward of 80-100,000 page requests per day and fairly complex
sql queries etc).
It would certainly make the install much more straightforward if I could
just use the i386 version of Etch, but if someone can tell me that there
really is substantial difference for LAMP type operation with AMD64,
then I'm all ears.
As for number of connections, I'm not all that concerned about that,
because by the time we get to hundreds of people hitting the modperl
backend, the server is swamped anyway and is CPU/IO bound.
I have the feeling that it certainly will be much faster for certain
types of app, but it is for LAMP specifically I am wondering.
Thanks,
/Neil
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