Questions[low-memory](server)

I, like many people, have a relatively out-of-the-box Apache installation with a lot of default "LoadModule" lines.

Since the beginning, I've installed a lot of software, and to be honest, I don't know what software is is using which modules.

I would like to reduce the memory footprint of my Apache instances, and to do that, I'd like to remove modules from being used. The only way that I know of to determine if a module is in use is to remove it from the configuration and see if anything breaks. This is bad in more ways than I have time to describe.

I would like to know if anyone is aware of a way to get Apache to report which modules have been used, or if there's another way to programmatically determine whether a module is safe to un-configure.

I'm finding that on occasion my Linux box runs out of memory and it starts tearing down random processes to deal with it.

I'm curious what administrators do to avoid this? Is the only real solution to up the amount of memory (will upping the swap alone help?), or is there better ways to set up the box with software to avoid this? (i.e., quotas, or some such?).

Every 10 seconds or so, both our web servers (windows server 2003, running iis6), report the same errors in the event log.

> Event Type:   Error Event
> Source:   Application Popup Event
> Category: None Event ID:  333
> Date:     2009-08-18 Time:        22:04:06
> User:     N/A Computer:   DFS273
> Description: An I/O operation
> initiated by the Registry failed
> unrecoverably. The Registry could not
> read in, or write out, or flush, one
> of the files that contain the system's
> image of the Registry.
> 
> For more information, see Help and
> Support Center at
> http://go.microsoft.com/fwlink/events.asp.
> Data: 0000: 00 00 00 00 01 00 6c 00  
> ......l. 0008: 00 00 00 00 4d 01 00 c0
> ....M..À 0010: 00 00 00 00 4d 01 00 c0
> ....M..À 0018: 00 00 00 00 00 00 00 00
> ........ 0020: 00 00 00 00 00 00 00 00
> ........

I can't find any information as to what could cause these kinds of errors. The CPU is quite busy at 90-100% but there is almost 1 GB of unused RAM.

I have a relatively small home Red Hat Linux server (about 8 GB RAM). I don't use it for much other than running some home grown apps to keep track of various things. The only real things running on the box are a database and a web server.

I've noticed that when checking system counters using tools like NMON and TOP that the total system free memory is relatively low (on the order of a few hundred MB), while the active memory for the database and web server is still low (only consuming a combined 3 GB). Even when including all other running processes the total consumed memory is less than 4 GB.

Why does Red Hat Linux report less free memory than the total memory minus the sum total of used memory of running processes?

How to minimize memory usage on LAMP? Virtual dedicated server, max 512 RAM, 20 GB drive space, it should run a Wordpress blog. Not sure for load, but lets say 2-5k visitors per day.