Linux in Large Corporations (Was: New to group)

[John (EBo) David]

George Toft wrote:
> 
> That was a bit of editing that somehow got my name attached.  I
> use VMWare with 128MB with no problems.

oops... the following statement was mine.  Writing a response to it is
on my ToDo list, so this has just prompted me to deal with it...

It is not how much memory I have at the moment (128MB, and planning to
upgrade today actually ;-)  It is an issue of how much physical/virtual
memory each process can cope with.  The newer kernals can deal with
processes that can use upto 64GB ram and many terabites of swap space (a
total of 64bis of address space).  The issue for me is that I am writing
and testing software that plays with LARGE datasets.  One in particular
is a 3 meter RGB image of almost the entirity of Maracopa county.  That
one image is 43,000 x 41,000 pixels or roughly a 3GB image.  It turns
out that the old kernal could only deal with 1GB Ram physical and 3GB
virtual address space...  So, to sidstep the issue I just used the 64GB
Kernal patches...  Now the problem is that VMWare cannot compile it's
drivers (which is done automatically when running vmware-config.pl)
because it does not support 64GB-kernals...

Here are some excerpts from online linux-mm.org documents:



[exerpts from http://linux-mm.org/]

As of 10/31/99 Linux (kernel >2.3.24) supports up to 64GB of physical
memory and up to several terabytes (that's no typo) of swap space. This,
of course, means that the Linux and >1GB of RAM HOWTO is now obsolete. 

Technical background

Since the x86 is a 32 bit machine, we are confined to 4 GB of address
space. Because of specific x86 MMU weaknesses (I've heard rumours that
SPARC/32 doesn't have this problem) we have to split up this space
between virtual and physical space. This means that when we choose a
larger physical space (to support more RAM) the maximum size of an
individual program gets smaller. 

Linux currenly uses a 3:1 virtual:physical split, meaning that the
kernel can use a maximum of 1 GB (minus 64 MB administrational overhead)
RAM and the maximum program size is 3 GB (some object-oriented databases
need this). You can change this to something else (eg. a 2:2 split if
you have 2 GB of RAM), but enlarging the physical space means
restricting the maximum size of your programs. 

The main reason that Linux uses a 3:1 split is that it gives us 3 GB of
virtual address space per process and most processes run faster when
they have a lot of virtual space to fool around in (no need to
constantly reshuffle data around to fit in other stuff). Another reason
is that we've always done this and there may be some old programs around
that break when we change it. Besides, large machines are (should be)
administrated by clueful sysadmins who can hack the kernel to fix
things... 

> "David P. Schwartz" wrote:
> >
> > "John (EBo) David" wrote:
> >
> > > George Toft wrote:
> > >
> > > I've had and have run VMWare for about a year and a half and am not
> > > satisfied with it...  I upgraded my Linux OS and now VMWare will not
> > > even load because I'm running dual processor and it cannot cope with the
> > > 64GB memory configuration...