Maximum amount of RAM

[dtipton]

Is there a maximum amount of RAM you can have installed on a redhat 7.1 server? Someone posted to the linux forum on www.oracle.com (http://www.oracle.com) that redhat can't use more than 1GB of RAM. They claim that the 2.4 kernel will cause a core dump if the OS tries to access a memory address higher than 1GB. I'd love to test this but the biggest box I have contains 256MB of RAM. We were planning on ordering a server with 3GB in the near future though.

Thanks,
Don

[Malakin]

The 2.4x kernel has support for up to 64GB memory support. I don't know how much memory the default RH 7.1 kernel has, I searched their site and it doesn't seem to say. Worse case scenario is you would have to recompile to support more, not a big deal.

Their server version clearly states that it supports up to 64GB of ram, but the description of the standard 7.1 says nothing. So maybe with the server version it would work just fine, but with the standard version you'd have to recompile, I'm heavily speculating here though :)

[ 06 September 2001: Message edited by: Malakin ]

[DMR]

In describing a server setup, this article (http://www.redhat.com/support/alex/160.html) from Redhat's support site has the following excerpt: A server using this configuration should have 1GB or more of system memory, so swap won't be a big issueWhile not stating the maximum amount of RAM, it does seem to indicate that a 1G limit isn't an issue. BTW- The article was written in the days of RH 6.2.

[Molecule Man]

I went to the linux source and found
Linux can use up to 64 Gigabytes of physical memory on x86 systems.
However, the address space of 32-bit x86 processors is only 4
Gigabytes large. That means that, if you have a large amount of
physical memory, not all of it can be "permanently mapped" by the
kernel. The physical memory that's not permanently mapped is called
"high memory".

If you are compiling a kernel which will never run on a machine with
more than 1 Gigabyte total physical RAM, answer "off" here (default
choice and suitable for most users). This will result in a "3GB/1GB"
split: 3GB are mapped so that each process sees a 3GB virtual memory
space and the remaining part of the 4GB virtual memory space is used
by the kernel to permanently map as much physical memory as
possible.

If the machine has between 1 and 4 Gigabytes physical RAM, then
answer "4GB" here.

If more than 4 Gigabytes is used then answer "64GB" here. This
selection turns Intel PAE (Physical Address Extension) mode on.
PAE implements 3-level paging on IA32 processors. PAE is fully
supported by Linux, PAE mode is implemented on all recent Intel
processors (Pentium Pro and better). NOTE: If you say "64GB" here,
then the kernel will not boot on CPUs that don't support PAE!

The actual amount of total physical memory will either be
auto detected or can be forced by using a kernel command line option
such as "mem=256M". (Try "man bootparam" or see the documentation of
your boot loader (lilo or loadlin) about how to pass options to the
kernel at boot time.)

If unsure, say "off".