FW: [olug] Possible error message

[Phil Brutsche]

Trent Melcher wrote:
> 
> -----Original Message-----
> From: Trent Melcher [mailto:tmelcher at trilogytel.com] 
> Sent: Tuesday, May 06, 2003 8:26 PM
> To: 'CM Miller'
> Subject: RE: [olug] Possible error message
> 
> 
> Yes, the gerenal rule of thumb is usually double the amount of RAM you
> have for swap.

That's an old rule of thumb that really doesn't necessarily apply to 
modern systems.  VM subsystems have improved quite a bit since the 1980s :)

Does a Linux firewall with 32 MB - one that's not running squid :) - 
REALLY need ANY swap, much less 64MB?  NO

Does that database server with 2GB RAM REALLY need that 4GB swap?  Well, 
maybe it does...

Does a workstation (ie MINE!) with 1GB+ RAM REALLY need 2GB+ swap?  NO

Does having swap help performance?  YES (at least, I've heard it does 
under Linux, I've never run without swap to find out)

YMMV, of course.  It all depends on the situation, and most of the ones 
I run into you do NOT *need* 2x RAM for swap.  99% of the time it's too 
much for the application (ie it's wasted disk space because it's never 
used), and the rest of the time it's way too little (mostly because the 
machine's owner doesn't want to spend the $35 to get that extra Crucial 
256MB DDR266).

> I cant remember exactly, but there is a 4 GB limitation for 32bit
> processors, it either on physical RAM or Virtual RAM, it may be both,
> havent looked it up in a while.

Without PAE, 4GB physical; 36GB physical with PAE.  PAE is this feature 
on PPro (maybe PII) and newer CPUs that changes memory addressing a 
little bit (36-bit addresses instead of 32-bit).

64GB total available address space.

That's with 32-bit ix86 processors, of course :)

-- 

Phil Brutsche
phil at brutsche.us