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Re: [vox-tech] Three Install Questions
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Re: [vox-tech] Three Install Questions



On Tue 22 Feb 05, 10:49 PM, Karsten M. Self <kmself@ix.netcom.com> said:
> on Mon, Feb 21, 2005 at 11:58:35AM -0500, Peter Jay Salzman (p@dirac.org) wrote:
> > 
> > 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 The "swap is double RAM" (hereafter "SIDR") rule is _really_ outdated.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 Peter, that's the myth (that 2x RAM is obsolete) I specifically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:

But the whole premise is that there's no NEED to add swap if there's no need
to add swap.  Ask yourself - why would a computer suddenly need more swap?

If your answer is "I dunno", then it simply makes no sense to "plan ahead".

OTOH, if your answser is "because within a week, this system will support
20 users, and if my advertising department does their job correctly, I hope
to have 200 users next month", then yeah, "planning ahead" makes a whole lot
of sense.

OTOH, if you're worried about leaky apps (which I've rarely seen on Linux,
although I'm sure they exist) then why not just tell Wilson to make larger
swap partitions?  Why should he have blank partitions for *future* swap
partitions for when he adds 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.
  
Not a convincing argument.

Your ears (and patience!) should determine how much RAM you need.  Not
price.  What's the point of the price argument if you have to wait 5 seconds
for firefox to become resident?

> 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.

I will, and will read it with an open mind.

> SIDR lives.

I certainly won't deny THAT fact.

It's very difficult to rip dogma out of our collective consciousness.


I have a system with 2GB of RAM.  This machine is a
gaming/playing/programming machine.  To date, I've NEVER seen even one byte
of swap used.  Not even one bit.  Not in the 2 years I've owned this
machine.

Are you seriously advocating that I should whip out partition magic and
create a 4 GB swap partition?

If so, I think we should just agree to disagree...   :) 

Pete

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