[vox-tech] Three Install Questions

[Karsten M. Self]

on Mon, Feb 21, 2005 at 11:58:35AM -0500, Peter Jay Salzman (p at dirac.org) wrote:
> On Mon 21 Feb 05,  7:39 AM, Wilson Shealy <wtshealy at comcast.net> said:
> > Hi everyone,
> > 
> > I appreciate all of the great suggestions I've received from this list.  It 
> > seemed appropriate that I should follow up with the practical solution to 
> > my problem,  
> > 
> > I never determined what the cause of my boot problem was but I did find a 
> > workaround.  I created a boot floppy and then copied the boot sector of the 
> > boot floppy into the root directory of my XP install as a binary file.  By 
> > pointing the windows installer at this binary file, it will now "boot" into 
> > GRUB which will load my Linux install.  
> > 
> > I don't know why this wasn't working when trying to copy the boot sector 
> > directly from the partition.  It may have something to do with the reiser 
> > file system but I really am only speculating.
> > 
> > As for swap space,  I've decided to go with Karsten's suggestion and create 
> > multiple swap partitions.  This way I can mount the additional swap after 
> > adding more RAM (probably next month).
> 
> Hi Wilson,
> 
> The "swap is double RAM" (hereafter "SIDR") rule is _really_ outdated.  I
> believe it even predates Linux.  At the very least, it predates when *I*
> started to use Linux.

Peter, that's the myth (that 2x RAM is obsolete) I specifically
addressed in my post.  Read it and Martin Pool's essay.  SIDR *is* a
decent rule of thumb.

Moreso because it's easy to increase RAM (drop in another DIMM).
Adding additional swap partitions is a PITA (more on why more memory =>
more swap below), so you might as well plan ahead.  My rule of thumb:

  - Create swap partitions sized to your current RAM allocation, max 2
    GiB per partition.

  - Create enough swap partitions to allow at _least_ 1x your system max
    RAM, preferably 2x system max RAM.  "System max RAM" is the maxiumum
    amount of memory supported by your system.

  - Allocate swap partitions to 2x current RAM.

<...>

 
> If your computer isn't using swap to begin with, there is no reason for you
> to increase swap.  

Largely correct, and this is where the discussion should focus:  how is
the system currently performing?   Are you constantly paging (bad:  need
more RAM) or running into OOM conditions (bad:  if not paging heavily,
more swap, if paging heavily, more RAM).

> With memory for home systems relatively cheap these days if you ever
> hear or see your computer swapping, go out and buy yourself another
> DIMM (if you're using Linux).

Right.

But swap is a fraction the cost of RAM.

   512 MiB DIMM:  ~$100 - 150.
   512 MiB swap:  ~$0.50.
 
> Don't think that your computer will magically need more swap just because
> you unscrew the case and stick another DIMM in there.   If you're dealing
> with like ... Ultrix from 1987, then yeah.  You'll need to increase swap.
> However, the truth of the matter is that when you stick a DIMM into a modern
> Linux system, your system will need LESS SWAP, NOT MORE, unless you start
> running extra applications just for the heck of it.

Oddly enough, this seems to be the case.

People run more apps.  "Because they can".  Personally, I hate having to
constantly close out big bloated processes -- usually my browser session
-- but also things like the GIMP, OOo, and mutt on huge folders.  

And the truth is that until their feet are held to the fire, apps
developers tend to ignore memory issues.  Just look at what your own
advice would be to someone planning on offering, say, a family legacy MS
Windows replacement desktop based on a PII-233 or worse, 65 MiB RAM or
worse.  While a 233 could handle load for most purposes, I'd be a lot
more comfortable at 128-256 MiB RAM, if not more.

Over time, memory, *and* swap requirements increase.  Economizing on
swap is IMO *extremely* false economy.  With a current system of 1 GiB
max RAM and 200 GiB disk, you're allocating *1%* of your disk to swap,
at 2x max RAM.  That's going to cost you ~$1-2 of disk storage (you're
losing far more in reserve and block allocation).  What you're buying is
insurance against OOM, as well as better kernel balancing of VM (Pool's
essay, I told you to read it already).  I say do it.

SIDR lives.
 

Peace.

-- 
Karsten M. Self <kmself at ix.netcom.com>        http://kmself.home.netcom.com/
 What Part of "Gestalt" don't you understand?
    You...display numerous pro-Microsoft bumper stickers ("Honk if you
    hate anti-trust laws") on your car.
    - http://mail.nl.linux.org/humorix/1999-11/msg00008.html
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