Re: Do I need 64Bit if RAM is more than 4 GB?
"Dirk H. Schulz" <dirk.schulz@kinzesberg.de> writes:
> Hi folks,
>
> I hope this is the right place for this kind of question:
>
> I want to run a server with more than 4 GB of RAM. I do not need
> applications/processes to address more than 4 GB each. Let's say I
> want to have 2 instances of apache on the machine, and each instance
> should address a max of 4 GB.
>
> Do I need a 64Bit Linux then? Or can I install a 32Bit Linux on a
> Server with 8 GB RAM, set up my 2 instances of apache, and that`s it?
>
> Sorry for that kind of basic question but I did not find any docs on
> that googling around.
>
> Thanks for any help and hint.
>
> Dirk
>
>
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You need 64bit address space inside the kernel. I386 has some hacks to
make this work up to 64GB ram on some hardware and I don't know if
amd64 cpus and motherboards can work the same way. The extra work
needed for the hacks makes this slower though.
The other way is to use an 64bit amd64 kernel to get 64bit addresses
directly. You then still have the choice of using a 32bit userspace
with its 2-4 GB limit per process or using a 64bit userspace.
As for having 2 insances of apache that could be trivial or
difficult. apache already forks
mrvn@dual:~% ps aux | grep apache
root 1817 0.0 0.0 141072 444 ? S Sep06 0:00 /usr/sbin/apache
www-data 1872 0.0 0.2 141204 1528 ? S Sep06 0:00 /usr/sbin/apache
www-data 1873 0.0 0.3 141204 1552 ? S Sep06 0:00 /usr/sbin/apache
www-data 1874 0.0 0.3 141204 1604 ? S Sep06 0:00 /usr/sbin/apache
www-data 1875 0.0 0.3 141204 1604 ? S Sep06 0:00 /usr/sbin/apache
www-data 1876 0.0 0.3 141204 1760 ? S Sep06 0:00 /usr/sbin/apache
www-data 2115 0.0 0.2 141204 1528 ? S Sep06 0:00 /usr/sbin/apache
www-data 2130 0.0 0.2 141204 1380 ? S Sep06 0:00 /usr/sbin/apache
www-data 16802 0.0 0.4 141204 2124 ? S Sep07 0:00 /usr/sbin/apache
but the chidren share memory and would have some overall limit below
4GB. And if you run 2 seperate apache servers they need to run on
different ports or interfaces.
Do you realy think apache needs that much ram? Don't you have a
database, php or cgi scripts running below apache that actualy eat all
the ram? In that case it might be wise to use a 64bit postgresql for
the extra address space while keeping the rest 32bit or something
similar.
Mix and mingle.
Goswin
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